Living With Climate Change

By Trevor Letcher

Living with Climate Change contains different topics on how to adapt to global warming. With a strong focus on ways of adapting to climate change, the book also examines the root causes of global warming. Readers are provided all the most up-to-date thinking and information on each issue due to the extensive list of references connected to each chapter. By linking various topics and interesting new innovations that are often synergistic, this book covers a wide range of issues in global warming adaptation that is ideal for readers from many disciplines.

• Covers ways of coping with global warming and climate change
• Contains the most up-to-date information on how to prevent the worst effects of global warming
• Discusses the connection of climate change to human health

• Language: English
• Publisher: Elsevier Science
• Release date: Dec 1, 2023
• ISBN: 9780443185144

Book preview

Section A

Introduction

Chapter 1 The root causes of global warming and the new normal

Trevor M. Letchera,b    a Emeritus Professor, University of KwaZulu-Natal, Durban, South Africa

b Stratton on the Fosse, Somerset, United Kingdom

Abstract

In this chapter, we look at: the root causes of global warming and the evidence that it is indeed the build-up of carbon dioxide that is the main driver for global warming; feedback mechanisms liable to exacerbate global warming; the present position with fossil fuels; the possible options we have in renewable and nonproducing CO2 energy systems; and the problems we are facing and will face as a result of global warming.

Keywords:

Global warming; Climate change; Root cause of global warming; Feedback mechanisms; Renewable energy option; Living with climate change

1 Our predicament

According to an ongoing temperature analysis, led by scientists at NASA's (National Aeronautics and Space Administration) Goddard Institute for Space Studies (GISS), the average global temperature on Earth has increased by at least 1.1°C (1.9° Fahrenheit) since 1880. The majority of the warming has occurred since 1975, at a rate of roughly 0.15–0.20°C per decade [1]. Furthermore, the latest assessments from the Intergovernmental Panel on Climate Change (IPCC) suggest that there seems to be no way to limit the global temperature rise of 1.5°C [2]. This will have major implications around the world, including droughts; dangerous levels of heat; floods; hurricanes and typhoons; environmental degradation; loss of animal, plant, and insect diversity; famine; disease; rising sea levels; rising mass migration; increasing economic instability due to crop failures; economic instability due to inequality and racial justice; failure to bring about effective global governance—all of which will trigger major societal upheavals. These extreme weather events are now being played out in most parts of the world.

All the evidence for global warming points to the recent rise in greenhouse gas (GHG) concentration and carbon dioxide in particular. Even if emissions of GHGs were stopped suddenly, the Earth's surface temperature would require thousands of years to cool down and return to a preindustrial level [3]. This is the raison d’être for this book. Humanity is in it for the long haul.

The IPCC has called on new tools to be deployed to help reduce global warming. The latest IPCC report (April 2022) focuses on five areas aimed at halving GHG emissions by 2030: reduce fossil fuel use; deploy renewable energy; adopt a circular economy; capture and store carbon; and create greener cities [4].

An independent group of scientists has created the Climate Overshoot Commission [5] to consider expanding and accelerating measures to reduce GHG emissions and climate vulnerability, remove excess carbon dioxide from the atmosphere, and look into the ethics and feasibility of new climate technologies, some of which are unproven and possibly dangerous at large scale, such as cooling the planet by reflecting incoming sunlight.

Billionaire Bill Gates, Microsoft's co-founder, is supporting a solar geoengineering project to dim the Sun's energy reaching the Earth with plumes of powdered chalk (CaCO3), released at an altitude of 12 miles [6]. There has been much opposition to this type of solar geoengineering as the consequences could be catastrophic [7].

Other ideas include constructing giant energy harvesting collectors in space and beaming the energy to Earth using microwaves [8], refreezing the Arctic [9], using genetic engineering to create super algae that could absorb CO2 more efficiently than natural algae [10], and growing zero-emission meat in petri dishes [11].

2 Why are we having global warming?

Air temperatures on Earth have been rising since the Industrial Revolution. While natural variability plays some part, evidence indicates that human activities—particularly emissions of heat-trapping GHGs (CO2 and CH4 to mention two of the three most important GHGs)—are mostly responsible for making our planet warmer. This is largely a result of the burning of fossil fuels in all its forms: coal, oil, and gas.

In order to understand why we are experiencing global warming, we must understand the significance of atmospheric vibrations. Energy from the Sun that reaches us is largely visible and ultraviolet in the frequency range of 2000–30,000 THz (2000–30,000 × 10¹² cycles per second). This energy heats up the seas and the Earth. The heated Earth radiates heat (black-body radiation) into outer space at a lower frequency range (0.3–400 THz). This radiant heat is largely in the infrared (IR) region of the electromagnetic spectrum.

Now, the molecules in the atmosphere—N2 (78%), O2 (21%), CO2 (0.042%), H2O (between 0% and 1%), and CH4 (1.7 ppm or 0.00017%)—are also in a state of vibration; for example, for the diatomic molecules, the N–N bond of nitrogen and the O–O of oxygen, vibrate with frequencies of about 1000 THz. These frequencies are outside the range of the Sun's radiation and also out of the range of the Earth's black-body IR radiation. For the polyatomic molecules, the bonds holding the atoms together, O–H for water, C–O in carbon dioxide, and C–H in methane, vibrate at a much slower rate than the bonds in the diatomic molecules and their vibrations are in the range of 10–300 THz. This is within the IR range of the radiant heat leaving the Earth but not in the range of the Sun's UV-visible radiation.

When the Sun's high-frequency rays shine on the Earth, they pass through the atmosphere and do not interact with the vibrating gaseous N2, O2, H2O, CO2, and CH4 molecules—their vibrating frequencies are much less than the frequencies of the incoming UV-visible energy from the Sun. Things are different for the IR black-body radiant energy leaving the Earth. This IR radiation has a similar frequency to the bonds of the polyatomic gases in the atmosphere and interacts sympathetically with these vibrating bonds, causing the bonds to increase their vibration and heat up. In a sense, the IR radiation has been blocked by the polyatomic gases, CO2, H2O, and CH4. This process of sympathetic absorption of energy is the same as the effect that the marching pace of an army can have on the natural frequency of a bridge and which, in extreme cases, can cause a bridge to vibrate violently and break. A case in point is the Millennium Footbridge in London. On the opening day in June 2000, the bridge was found to vibrate dangerously (natural frequency 1.3 Hz) in sympathy with walkers walking at the same pace [12]. It was closed for modifications and repairs and opened again almost two years later.

With IR radiation, the excited polyatomic species then their excess energy, heating up the gases in the atmosphere, which in turn heats up the oceans and results in an increase in water evaporation and an increase in the water molecules in the atmosphere. This leads to further warming of the atmosphere and planet. This process has been going on for millions of years and has helped to keep our planet 33°C warmer than it would be without the gases [13].

Over the past 200 years, the concentration of CO2 in the atmosphere has increased by 50% from 280 ppm (preindustrial atmosphere) to 421 ppm [14]. It has been estimated that CO2 is responsible for 30% of our present global warming and H2O for the remaining 70%. The increase in the concentration of carbon dioxide in the atmosphere has merely been the trigger for our present global warming of 1.1°C. The effect of CO2 as a controller of the Earth's temperature can be demonstrated very simply [15].

The effect that CO2 was responsible for keeping the Earth warmer than it would otherwise be was first demonstrated by Tyndall in 1861 [16,17].

The contribution of CH4 to global warming is not as important as the contribution of CO2, in spite of its global warming potential being 25 times that of CO2 [18]. However, the concentration of CH4 in the atmosphere is very much lower, although it is also rising at an alarming rate with its concentration more than doubled since preindustrial times. The methane atmospheric concentration is now about 1800 ppb (0.00018%) and is almost 250 times lower than that of CO2 [19].

3 Can we prove that global warming is due to carbon dioxide?

We have no way of proving, categorically, that climate change and global warming are due to the rise of GHGs and CO2 in particular. We cannot suddenly switch off the production of anthropomorphic-generated carbon dioxide. Moreover, as the CO2 in the atmosphere is very slow to decompose, this experiment would take hundreds of years.

The most compelling evidence that the increase in CO2 is the most likely cause of global warming can be seen in the related graphs of CO2 concentration in the atmosphere and the global average temperature as functions of time over the past many decades (see Figs. 1 and 2). The CO2 increase is mirrored by a rise in the relative increase in average global temperatures over the past 60 years.

Fig. 1

Fig. 1 The Keeling Curve showing the increase of CO 2 concentration from 1958 to 2021 [20]. Data from Dr. Pieter Tans, NOAA/ESRL and Dr. Ralph Keeling, Scripps Institution of Oceanography. Thanks to the National Oceanic and Atmospheric Administration (NOAA) for providing the data, https://en.wikipedia.org/wiki/Keeling_Curve.

Fig. 2

Fig. 2 The relative increase in the world's average surface air temperature from 1880 to 2019 [21]. Original data produced by ASA's Goddard Institute for Space Studies, http://data.giss.nasa.gov/gistemp/graphs/.

Another question which needs answering is: Is the CO2 increase due to human activity? The evidence that it is indeed due to human activity is based on the relative ratios of carbon isotopes. The relative amount of ¹³C in the atmosphere has been declining and that is because the ratio of ¹³C in fossil-fuel-derived CO2 is significantly lower than the CO2 produced from present-day decaying plants [22].

People do ask the question: Is climate change not due to natural causes, as has happened millions of years ago? All the evidence of natural causes—including variations in the Sun's output, variations in the Earth's orbit around the Sun, and volcanic eruptions—has shown that these causes have yielded little surface warming, or even a slight cooling, over the 20th century [23].

4 Feedback mechanisms and why global warming will get worse

One of the truly frightening aspects of climate change is the possibility of a rapid escalation of global warming, as a result of tipping-point phenomena. These phenomena involve feedback mechanisms, which enhance global warming. The absorption of IR radiation by CO2 molecules, which results in increased water vapor in the atmosphere, and a subsequent increase in the absorption of IR energy, is one feedback mechanism and was discussed earlier. Another of these feedback mechanisms involves the melting of glacial and ice sheets. When ice melts, land or open water is exposed and both land and open water are much less reflective than ice. As a result, both the land and water heat up, and this in turn causes more melting and so the cycle continues.

The oceans contain vast amounts of dissolved CO2. The amount is governed by the solubility of CO2 in seawater which is dependent on temperature. With global warming, the oceans become warmer, resulting in a lowering of the CO2 solubility and leading to some CO2, leaving the oceans and entering the atmosphere, which in turn increases global warming in an ever-increasing cycle.

Another feedback mechanism is at play in the peat bogs and permafrost regions of the world, such as Siberia and Greenland. Rising global temperatures are melting the permafrost and heating peat bogs, resulting in a release of methane gas. Methane is also a powerful GHG and is very effective at trapping the IR radiation leaving the Earth. In spite of the present low concentration of CH4 in the atmosphere, its concentration is rising rapidly. This poses a real threat for our future [24].

Yet another feedback mechanism involves methane clathrates, a form of water ice that contains methane within its crystalline structure. Extremely large deposits have been found under the sediments of ocean floors. An increase in temperature breaks the crystal structure, releasing the caged methane. Rising sea temperatures could cause a sudden release of vast amounts of methane from such clathrates and result in runaway global warming.

5 We are not coping with global warming because we are not reducing our reliance on fossil fuel

A summarized set of global energy consumption data for the years 2000 and 2021 is given in Table 1 [25].

Table 1

Over the past 21 years, coal consumption has increased by 62%, oil has increased by 19%, and gas by 68%, in spite of a major deployment of renewable energy: hydropower has increased by 43%, wind-generated power has increased by fiftyfold, and solar by ninetyfold, while other renewable forms have increased by fourfold. At present, global wind power stands at about 840 GW and solar at 1000 GW. Assuming that an ordinary coal-powered power station is rated at about 1 GW, the present wind- and solar-produced energy is a significant contribution to world energy. However, this recent explosion in renewable wind and solar energy has had little impact on the amount of fossil fuel we are still using. It appears as though the more we develop and deploy new renewable forms of energy, the more energy we use globally. That has probably been the case for energy ever since fire was discovered and steam power was invented.

6 What should we do to reduce global warming?

To reduce global warming, there are two main things we can do: reduce our reliance on fossil fuels in all its forms and remove CO2 from the atmosphere. Presently, we use fossil fuel for producing electricity; transport; industry, including cement and steel-making; residential (including heating and wood fires); and agriculture. Fossil fuels are the main producers of CO2. The overall global breakdown of CO2 emissions is given in Table 2.

Table 2

https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions.

As is evident in the previous section, we are not making much headway in replacing fossil fuel with renewable forms of energy. Even if we did replace coal-powered power stations with renewable energy, doing so would only take care of the 27% of carbon dioxide emissions and part of the 12% from residential heating and cooling. It would also help to reduce the 28% of emissions from transport, assuming we invest heavily in both electric cars and hydrogen production for powering heavy vehicles and possibly powering large ocean-going ships (using perhaps NH3) and even powering airplanes.

The removal of CO2 from the atmosphere is even more difficult but equally important, especially as the CO2 naturally remains in the atmosphere for a very long time, unless we remove it. The half-life of CO2 in the atmosphere is about 100 years [18].

Carbon dioxide is a very stable gas and does not readily react with other chemicals. This can be inferred from its large negative standard Gibbs energy of formation (ΔGf = −393.5 kJ mol−1), implying that for CO2 to react with another chemical, a significant amount of energy must be supplied. Hence, its build-up in our atmosphere over many years.

The situation with CH4 is not as serious as it is with CO2 as CH4 is more dilute in the atmosphere (0.0002%) and is also a more reactive gas (ΔGf = −50.5 kJ mol−1), and thus does not remain in the atmosphere for as long as CO2. The half-life of CH4 in the atmosphere is 8.6 years.

There are two technologies aimed at capturing CO2, and they both use similar techniques. Direct air capture and storage (DACS) removes carbon dioxide from the air, while carbon capture and storage (CCS) helps to reduce emissions at the point of source because it prevents new fossil-fuel-produced CO₂ from entering the atmosphere.

Removing CO2 from the air using the DACS process is costly as a result of the low concentration of CO2 in the atmosphere (0.04% by volume and by number of molecules). Today, two technological approaches are being used to capture CO2 from the air: liquid and solid DACS. Liquid systems pass air through chemical solutions (e.g., a hydroxide solution or an amine solution, which removes the CO2, based on the high solubility of CO2 in these solutions). The system reintegrates the chemicals back into the process by applying high-temperature heat while returning the rest of the air to the environment [27]. Solid DACS technology makes use of solid sorbent filters that chemically bind with CO2. When the filters are heated and placed under a vacuum, they release the concentrated CO2, which is then captured for storage or use.

Carbon capture and storage (CCS) of CO2 usually refers to the removal and storage of CO2 from industrial plants producing CO2 such as coal-powered power stations, cement factories, steel-making factories, and oil and gas plants, where the CO2 concentrations are very high. This technology uses the same CO2 capture processes used in DACS plants.

For both CCS and DACS processes, the captured CO2 can be transported in gaseous or liquid form to geological sites or to disused oil wells by tanks, pipelines, or by ships. Liquid CO2 occupies much less volume than its gaseous form, which is why it is often compressed into a liquid state before being transported. Pipelines are—and are likely to continue to be—the most common method of transporting the very large quantities of CO2 involved in both CCS and DACS.

There are many processes around the world capturing CO2 from the air. In 2021, there were 19 DACS plants operating worldwide, capturing more than 0.01 Mt CO2 per year, and a 1 Mt CO2 per year capture plant is in advanced development in the United States. The latest plant to come online, in September 2021, is capturing 4 kt CO2 per year for storage in basalt formations in Iceland. In the net-zero emissions program, DACS is scaled up to capture more than 85 Mt CO2 per year by 2030 and ∼980 Mt CO2 per year by 2050. This level of deployment will require several more large-scale demonstrations to refine the technology and reduce capture costs [27]. Even this, almost gigatonne of CO2, is small (less than 3%) compared with the amount of CO2 emitted in 2021 from burning coal, oil, and methane gas: 33.5 Gt y−1 (33.5 billion tons per year or 33.5 × 10⁹ t y−1) [28].

Achieving net-zero emissions around mid-century and containing temperature increases to well below 2°C will require the rapid deployment of all available abatement technologies as well as the early retirement of some emission-intensive facilities and the retro-fitting of others with technology like CCS. Carbon dioxide capture and storage will also be required at large scale as overshooting carbon budgets is, regrettably, almost assured. According to the IPCC 1.5°C Special Report, somewhere between 350 and 1200 gigatons of CO2 will need to be captured and stored this century. This equates to somewhere between 10 and 35 times our annual global CO2 emissions from fossil fuels. Currently, some 40 Mt of C02 are captured and stored annually from CCS processes, equivalent to about 0.1% of our current emissions. However, the deployment of CCS facilities around the world is growing. In 2021, there were 135 commercial CCS facilities in the project pipeline (27 are fully operational) from a diverse range of sectors, including cement, steel, hydrogen, power generation, and direct air capture [29]. Moreover, in every part of the CCS value chain, substantial progress is being made. New, more efficient and lower cost capture technologies across a range of applications are changing the outlook of this important contribution to solving the global heating problem [30]. But realistically, we have a long way to go to meeting the scenarios laid out by the IPCC.

7 Who is the main coal user in the world?

Coal is still one of the major global energy sources and China uses more coal than any other country and indeed today it uses over half the world's supply of coal. This has not changed much over the past 21 years; see Table 3 and Ref. [31a]. Coal is particularly bad for the environment because burning it produces not only CH4 but COx, NOx, SOx, and particulate material [31b].

Table 3

https://iea.org/data-and-statistics/charts/globl-coal-consumption-by-region-2000to2021.

8 What renewable energy is available for our use?

The simplest answer to the question of what renewable energy is available to replace fossil fuel is solar energy. This includes: direct energy from the Sun; wind energy, which is a secondary effect of solar energy; hydropower, which depends on rain which in turn depends on solar energy; tidal energy, which depends partly on wind; wave energy which also depends partly on wind; and biomass, which also depends on solar energy. Other nonproducing CO2 forms of energy include: nuclear (fission) and geothermal energy. These have been discussed in Ref. [32].

A summary of the types of nonproducing CO2 forms of energy available is given below. The number of options is encouraging but not all will appeal to every country. The future of power production in the future will almost certainly show a regional bias with solar energy developed between the tropics; wind in the Roaring Forties latitudes; hydropower in mountainous regions; geothermal energy in seismically unstable regions; and tidal energy in the few places in the world that are blessed with abnormally large tidal ranges.

Linked to renewable and intermittent forms of energy is the need for storing energy. Again, there are a number of options: pumped hydopower, gravitational storage (lifting heavy blocks), compressed air storage, liquid air energy storage, flywheels, rechargeable Li-ion batteries, Li-S batteries, Na-S batteries, Vanadium redox flow batteries, super capacities, phase change and molten salts storage, and hydrogen production and storage [33].

In an ideal world, with a massive renewable energy industry, producing hydrogen from excess renewable energy would allow, not only storage of energy (possibly in disused salt caverns), but H2 could be piped into houses for heating, used in factories, and used in cement- and steel-manufacturing. That would solve many problems, including the storing of energy.

9 Summary of the basic energy options, which do not produce CO2

(a)Solar photovoltaic: The solar photovoltaic (PV) cell was only invented in 1954 (Bell labs in the United States) and has become one of the mainstays of renewable energy. Sunlight, striking very pure silicon doped with phosphorus or boron, will create electrons which can be channeled into forming an electrical current. To date, solar photovoltaic electricity makes up about 7% of all electricity produced worldwide [34a]. It is relatively cheap and relatively efficient, and large solar farms can be erected in a relatively short time (months rather than decades). Total global solar PV capacity is 1 000 GW (1.0 TW) in 2021 and expected to be 2.3 TW by 2025 [34b]. The leading solar-energy-producing countries are: China 36%, USA 11%, Japan 7%, and Germany 7%. The largest solar farm is in India (the Bhadla Solar Park of 2.1 GW). A farm of 10 MW requires 30,000 panels with each panel producing 350–400 W, over a total area of 20 hectares.

(b)Concentrated solar power (CSP) and solar water heaters: The most efficient concentrated solar thermal energy is done using large parabolic mirrors to focus the Sun's energy. In this way, water can be made to boil, with the resulting steam used to make electricity in the usual way using turbines. To date, the total global capacity is 10 GW with Spain leading (3 GW) followed by the United States, Middle Eastern countries, and South Africa (0.5 GW). The deployment of CSP is small—about 1% of all solar energy—but it is versatile as the process can also be used to store energy either through heating a substance or perhaps chemically making ammonia or hydrogen which can be stored easily.

On a simple small household scale, solar thermal energy can be used to heat water for household use. In 2020, the global solar-water-heating capacity was over 500 GW of thermal energy. China is the world leader with 70% of the world's capacity [35].

Israel is the front-runner when it comes to building codes for solar thermal energy. In 1980, it was the first country worldwide to pass a solar building law, making it mandatory for new buildings of a certain height to have solar thermal units [36].

(c)Wind: This form of energy is a secondary effect of solar energy, but in certain parts of the world, it can be harnessed to great effect. At the moment, wind energy and solar energy contribute about10% to global electricity production [34a]. There has been exponential growth in wind turbine deployment, and the industry had grown from 14 GW in 2000 to 154 GW in 2016 and to 837 GW by the end of 2021 [37]. Most wind turbine schemes (96%) are located onshore, but this is rapidly changing. China and the United States are leaders in onshore wind turbines, and China and the United Kingdom are the leaders in offshore wind turbines. The latter is due largely to the shallow coastal waters of both China and the United Kingdom (less than 40 m deep). The United Kingdom has the largest offshore wind farms in the world—2.4 GW-at Hornsea One and Hornsea Two [38a]. The largest onshore wind farm (opened in 2021) is in China (Jiuquan Wind Power Base, Gansu Wind Farm in the Gobi desert) and is rated at 10 GW with plans to extend the capacity to 20 GW.

The energy produced by a single wind turbine is a function of the area created by the turning blades and that is related to Πr². Hence, the energy from a turbine increases as a function of r². Offshore wind turbines are becoming more important than onshore wind turbines. There are a number of reasons for this and the main one is that larger turbines can be erected offshore than can be manufactured and erected onshore. It is impossible to transport very large turbine blades on the roads and the very large blades can be made offshore in much the same way as oil rigs are constructed.

Wind turbines are difficult to install, especially offshore turbines. They also require significant maintenance as they suffer wear and tear. On the contrary, a solar panel will produce a more predictable output than a wind turbine, is fairly simple to install, and requires very little maintenance once installed. The main benefit of wind over solar is that turbines can generate power 24 hours a day and this is especially true for offshore turbines.

Modern offshore wind turbines are 190 m tall with blades of 80 m. One rotation can supply the daily energy of an average UK house. Each turbine is rated at between 3 and 10 MW so at least 100 turbines are needed to produce 1 GW.

(d)Hydropower: Hydropower or hydroelectricity refers to the conversion of mechanical energy from flowing water electricity by spinning rotors and turbines. It is considered a renewable energy source because the water cycle is constantly renewed by the Sun. Historically, one of the first uses of hydropower was for mechanical milling, such as grinding grains. Hydropower is the largest contributor of all renewable energy sources (60%) and accounts for almost 16% of worldwide electricity production. Major growth of this mature technology is not likely as many countries have exhausted the useful sites. The global hydropower capacity was 1.3 TW in 2019, with China being the leading country with a capacity of almost 350 GW [38b].

There are three main types of hydropower plants.

Impoundment facilities are the most common technology which use a dam to create a large reservoir of water. Electricity is made when water passes through turbines. China has four major hydropower dam projects producing 50 GW of electricity with the Three Gorges Project being the largest in the world and rated at 22.5 GW. Norway's topography lends itself to dams and hydropower, and 92% of Norway's electricity (40 GW) is produced from hydropower [38b].

Run-of-river facilities rely more on natural water flow rates, diverting just a portion of river water through turbines, sometimes without the use of a dam or reservoirs. Since run-of-river hydro is subject to water variability, it is more intermittent than dammed hydropower.

Pumped storage hydropower, or PSH facility, is able to store the electricity generated by other power sources, like solar, wind, and nuclear, for later use. These facilities store energy by pumping water from a reservoir at a lower elevation to a reservoir at a higher elevation. It is used in many parts of the world to store energy (potential) during times of cheap electricity or when there is an oversupply of electricity.

(e)Wave power is dependent on wind (which in turn depends on the Sun's energy), shape of coastlines, and tides (moon's gravity pull). Water does not actually travel in waves. Waves transmit energy, not water, across the ocean and, if not obstructed by anything, they have the potential of traveling across an entire ocean basin. A number of countries have begun to develop wave energy projects and these include Israel, Australia, Germany, Sweden, the United States, and the United Kingdom [39,40].

There are three basic designs being tested for wave-power generators: oscillating water columns, oscillating body converters, and overtopping converters. No significant deployment of wave machines for producing electricity has been reported.

(f)Tidal: Because the gravitational pull of the moon is weaker on the far side of the Earth, the ocean bulges out and high tide occurs. As the Earth spins, different areas of the planet face the moon, and this rotation causes the tides to cycle around the planet. Also, the shape of the continents influences the height of the tides, resulting in some places having a very small tidal difference between high and low tide (almost zero in some cases). Other places can have exceptionally high tides. Places with high tides are the Bay of Fundy between Nova Scotia and Brunswick in Canada (mean tidal range is 12 m), River Severn in, Bristol, the United Kingdom (10 m) and Dio Gallegos in Argentina (9 m).

Tidal energy has the potential to provide hundreds of gigawatts of power worldwide; the United Kingdom and the United States have said that these technologies could provide 20% and 15% of their electricity consumption, respectively. In spite of significant investment by many countries in tidal energy systems, the power generated from the ocean is minuscule. The reason for the lack of development is the large upfront construction cost [41,42].

The technology is based on the difference in height between a reservoir and the sea as tides ebb and flow. When the tide is coming in, the water on the sea side of the barrage is higher than the estuary side and water will flow from the sea side through the turbine into the estuary. When the tide is going out, the exact opposite occurs. The first power plant to use the technology was built on the La Rance River in France in the 1960s and is rated at 240 MW. Another operating tidal power station is in Sihwa, South Korea, where the 254-MW unit has been operating since 2011.

After much discussion, the UK government in 2013 decided not to go ahead with a proposed River Severn Barrage. The reasons given were high costs and environmental concerns. The United Kingdom is still pursuing other tidal projects. The country has approved a new design for tidal-power generation off the Scottish coast. Instead of being part of a barrage, these windmill-like turbines are fixed in an array to the seabed. The turbines will spin in one direction as the tide goes out and in the opposite direction when the tide comes in. The design looks like a submerged version of an offshore wind farm. The project is rated at about 400 MW [43a].

(g)Biomass: Biomass makes up a substantial fraction (14%) of the world's primary energy for electricity production, heating, and cooking [43b]. The global capacity of bioenergy electricity plants is about 140 GW, with China having the largest capacity of 22.5 GW [44,45].

In the United Kingdom, the largest power station using biomass is Drax and is rated at 2.6 GW. The fuel used at Drax power station is compressed wood pellets sourced from sustainably managed forests in the United States, Canada, Europe, and Brazil, which are largely made up of low-grade wood produced as a by-product of higher value wood products, such as lumber and furniture.

(h)Geothermal: Geothermal energy is derived from thermal energy that is contained beneath the Earth's crust. To produce electricity, wells are drilled into underground reservoirs to access the steam that then drives the electricity generators [46].

Iceland is a pioneer in the use of geothermal energy for space heating and geothermal power stations and currently generates 25% of the country's total electricity production in this way [47].

The global geothermal energy capacity was 15.6 GW in 2021 [48]. The main countries deploying geothermal energy are the United States (3.7 GW), Indonesia (2.1 GW), and the Philippines (1.9 GW). Other countries that have developed geothermal energy include Turkey, New Zealand, Mexico, Italy, Kenya, Iceland (0.8 GW), and Japan [49].

(i)Space solar: This involves focusing sunlight outside of our atmosphere (where it is greater than on Earth and shines continuously) and beaming it down to Earth by microwave. NASA is looking into this approach [8].

(j)Nuclear fission: The present-day nuclear industry is based on uranium 235. Other radioactive materials, such as thorium, can also be used. The total world nuclear energy capacity is about 400 GW. The world leaders in nuclear power generation are the United States (95 GW), France (62 GW), China (52 GW), Russia (29 GW), and the United Kingdom (7 GW). A nuclear reactor is driven by the splitting of atoms, a process called fission, where a particle (a neutron) is fired at an atom, which then fissions into two smaller atoms and some additional neutrons. Some of the neutrons that are released then hit other atoms, causing them to fission too, and releasing more neutrons. This is called a chain reaction.

The fissioning of atoms in the chain reaction releases a large amount of energy as heat. This heat is removed from the reactor by a circulating fluid, typically water, which can then be used to generate steam, which in turn drives turbines for electricity production.

In order to ensure the nuclear reaction takes place at the right speed, reactors have systems that accelerate, slow, or shut down the nuclear reaction and the heat it produces. This is normally done with control rods, which typically are made out of neutron-absorbing materials such as silver and boron.

There has been much discussion about small modular reactors which might one day partly supersede the present-day large nuclear power stations. Their capacity is usually less than 300 MW. They are designed to be cheaper, quicker, and less financially risky to build and are particularly good for remote areas. Similar small reactors are currently used in submarines.

(k)Nuclear fusion: This refers to the fusion of deuterium (one proton and one neutron) and tritium (one proton and two neutrons) to form helium (two protons and two neutrons) and a neutron plus energy (E=mc²) In the core of the Sun, huge gravitational pressures allow this to happen at temperatures of around 10 million Celsius. At the much lower pressures that are possible on Earth, temperatures to produce fusion need to be much higher—above 100 million Celsius.

No materials exist that can withstand direct contact with such heat. So, to achieve fusion in a lab, scientists have devised a solution in which a super-heated gas, or plasma, is held inside a doughnut-shaped magnetic field (made of beryllium and tungsten).

The Joint European Torus, sited at Culham Centre for Fusion Energy in Oxfordshire, has been pioneering this fusion approach for nearly 40 years. And for the past 10 years, it has been configured to replicate the anticipated ITER set-up in France and is supported by many governments around the world.

The approach to achieving fusion energy in the United States is different to that under investigation in the United Kingdom and in France. The National Ignition Facility in Livermore, California, uses 192 ultraviolet laser beams, focused on a target (a gold cylinder) that is smaller than a pencil eraser. The beams hit the target with around 1.9 megajoules of energy in less than four-billionths of a second, creating temperatures and pressures seen only in stars and thermonuclear bombs. The cylinder, which holds a frozen pellet of deuterium and tritium, collapses as the hydrogen isotopes at the pellet's core heat up, fuse, and generate helium nuclei, neutrons, and electromagnetic radiation. The goal is to unleash a cascade of particles that leads to more fusion and more particles, thus creating a sustained fusion reaction. By definition, ignition occurs when the fusion reaction generates more energy than it consumes [50].

In short, we have a surfeit of renewable options. Some are proving to be wonderful but others with great potential, such as tidal and wave energy, still need to be researched and tested and, if suitable, deployed.

10 What can we expect from global warming?

The 2022 IPCC report makes it clear that we are not coming to terms with global warming and that GHG concentrations in the atmosphere will continue to increase unless our annual emissions decrease substantially. Increased concentrations are expected to: increase global warming and duration and the frequency of heat waves; change our patterns of rainfall, creating floods and also droughts; raise the level of our oceans; increase the frequency, duration, and intensity of extreme events; shift ecosystems resulting in crop failure and famine; impact on human health with an increase in diseases and viruses (both old and new); increase the melting of ice, snow, and permafrost; and increase the acidity of our oceans. These changes will precipitate political upheavals, economic instability, major migration, conflicting views on ethics and justice, and possibly wars [51,52].

A more detailed list of the effects of global warming are presented below:

•Heat waves: Global warming is causing extreme heatwaves in most parts of the world. Recently, Australia battled its largest bushfire on record, California has experienced its worst fire season since records began; Oregon and Washington saw a spike in large wild fires in 2020; the Amazon faced its third largest fire on record while intense blazes have raged in Indonesia; and Siberia had some extreme wild fires as did central Asia and even parts of the Arctic [53]. Forest fires continue to increase year on year [54].

•Increased crop failures: The world is presently over-producing food in spite of over 800 million people going hungry [55,56a]. Our inability to feed the world's entire population is mostly due to food waste, food distribution, and a lack of infrastructure. However, over the past decades, many countries have experienced serious crop failures as a result of global warming, and computer models are predicting increasing crop failures in major bread baskets around the world [56b].

The war in Ukraine, resulting in a massive drop in the export of grain to the world, has highlighted the vulnerability of our food distribution. It is, as always, the poorer, the drought-ridden or flood-prone countries, that suffer the most from crop failure and food distribution.

•Droughts: Global warming is making droughts more frequent, severe, and pervasive [57]. Predictions for countries that presently experience regular droughts, such as parts of the United States and sub-Saharan Africa, can expect increased droughts. A recent report from the United Nations Convention to Combat Desertification stated that by 2030, an estimated 700 million people will be at risk of being displaced by drought [58].

•Floods: Flooding around the world has become more common over the past few decades. Hotter air can hold more moisture. If the air has an unlimited water supply, such as an ocean, then warmer air draws up extra moisture. This results in clouds containing a greater number of larger rain droplets and can be why showers in summer are often heavier than in winter. As the climate continues to warm, this effect will increase and heavy rainfall events are expected to become more common [59].

•Sea level rising: Long-term measurements of tide gauges and recent satellite data show that the global sea level is rising, with the best estimate of the rate of global average rise over the last decade being 3.6 mm per year (0.14 in. per year). This sea-level rise has been driven by: the expansion of water volume as the ocean warms; the melting of mountain glaciers in all regions of the world; and mass losses from the Greenland and Antarctic ice sheets [60].

In the United States, almost 30% of the population lives in relatively high-population-density coastal areas, where sea level plays a role in flooding, shoreline erosion, and hazards from storms. Globally, eight of the world's 10 largest cities are near a coast, according to the UN Atlas of the Oceans [61].

The country that will be most affected will be the Maldives, an island nation of 1,200 islands with a population of 540,000. It has an average elevation of less than 1 m. Kiribati in the Pacific is another island nation (with a population of 120,000) that is in dire straits if the sea level continues to rise. The average elevation is less than 2 m. Other countries that will he hard hit by sea level rises include China, Vietnam, Japan, India, Bangladesh, Indonesia, Thailand, and the Netherlands [62].

•New diseases and viruses: Increasing temperatures are being experienced in tropical areas where diseases such as malaria and dengue fever thrive. Increased flooding and drought will also raise the risk of disease as a result of unclean water. Further urbanization and migration related to climate change will also complicate disease prevention and control [63].

•Conflicting views on ethics and justice: Any action on climate change confronts serious ethical issues of fairness and responsibility with regards to individuals, nations, generations, and the environment. How these issues are dealt with could lead to serious conflicts [64].

•Wars: The lack of food security and access to clean water are known drivers of conflict with the potential to break out into wars. Nowhere is this more true than in Syria and in parts of the Middle East [65] and in Afghanistan. It is important to note that climate change by itself has not been proven to increase the likelihood of discord; however, climate change compounded with challenging economic, political, or social conditions can precipitate conflict. Climate change can be considered a threat multiplier, which means it amplifies problems already facing the world. Stressors such as poverty, political instability, and crime are magnified by increased droughts, floods, or heat waves.

•Increasing global economic instability: We can expect economic instability as a result of crop failures, migrations, insurance issues, and the collapse of businesses as a result of changing dynamics (for example, the abandonment of fossil fuels and the rise of renewable forms of energy). Developing countries such as those in Africa, with few resources to cushion catastrophes, are in line for major upheavals. It is the same story being played out repeatedly: those countries that have done the least to create global warming are having to bear the brunt of the consequences.

•Environmental degradation: We can expect further environmental degradation and resource depletion as a result of soil degradation, forest fires, impacts on plant, animal and insect life from heatwaves and flooding, each one creating tipping points for further environmental destruction.

•Insurance issues: Insurance companies face the dual challenge of addressing escalating climate change risks and shifting industry regulations [66,67].

•Rising migration: Climate change is a new driver of human migration that many people expect will dwarf all others in its impact. While the effects of climate change on migration have generated significant attention, little attempt has been made to ascertain just how many migrants are indeed climate-refugees. Displacement is almost always a result of a complex mix of factors; people adapt to changes and governments (and a few other powerful actors) and can influence what kind of movements take place in response to environmental changes [68].

It is very likely that the regions between the 45-degree parallels north and south will bear the brunt of global warming and that the major migration routes for displaced people will be from this region to regions north or south of the 45-degree parallels. These regions will include Canada, Europe, New Zealand, Chile, Argentina, Mongolia, Iceland, Greenland, China, and Russia.

•Escalating sea pollution—acidification: Ocean acidification has been called the chemical crisis of the global climate. Alongside global warming, ocean acidification risks pushing marine life beyond catastrophic limits. Since industrialization, the acidification of ocean surface water has increased by almost 30%. Coral reefs will be one of the most immediate victims of climate change if we do not take action very quickly. Although coral reefs make up just 1% of the surface of the oceans, as much as 25% of marine species are dependent on them. The breakdown of coral reef ecosystems also affects the protection of coastal zones, fisheries, and tourism. Without a drastic reduction in carbon dioxide emissions, by 2050, almost all of the world's coral reefs may have been subjected to such acidic conditions that they will be able only marginally to form calcium and continue growing [69,70].

References

[1]https://data.giss.nasa.gov/gistemp/.

[2]https://www.ipcc.ch/sr15/chapter/spm/.

[3]https://royalsociety.org/topics-policy/projects/climate-change-evidence-causes/question-20/.

[4]https://www.ipcc.ch/report/ar6/wg3/.

[5]https://www.overshootcommission.org.

[6]https://www.forbes.com/sites/davidrvetter/2022/01/20/solar-geoengineering-why-bill-gates-wants-it-but-these-experts-want-to-stop-it/?sh=5fe77c5f1842.

[7] Haywood J. In: Letcher T.M., ed. Climate Change: Observed Impacts on Planet Earth. third ed. Oxford, UK: Elsevier; 2021 Chapter 30, page 657.

[8] Jaffe P. In: Letcher T.M., ed. Future Energy: Improved, Sustainable and Clean Options for Our Planet. third ed. Oxford, UK: Elsevier; 2020 Chapter 24.

[9]https://www.newscientist.com/article/mg24332450-700-refreezing-the-arctic-how-to-bring-the-ice-back-with-geoengineering/.

[10]https://qz.com/1718988/algae-might-be-a-secret-weapon-to-combatting-climate-change/ ; and zero-emission meat grown in petri dishes.

[11]https://www.openaccessgovernment.org/meat-in-a-petri-dish/105115/.

[12] Dallard P., Fitzpatrick A.J., Flint A., et al. The London Millennium Footbridge. In: The Structural Engineer. . 2001;vol. 79/22 (20 November 2001).

[13]https://education.nationalgeographic.org/resource/greenhouse-effect.

[14]https://www.smithsonianmag.com/smart-news/carbon-dioxide-levels-now-higher-than-ever-in-human-history-180980229/.

[15]https://www.youtube.com/watch?v=Ge0jhYDcazY.

[16] Tyndall J. On the absorption and radiation of heat by gases and vapours. Philos. Mag. Ser. 4. 1861;22:169–194 273-85.

[17] Tyndall J. On radiation through the Earth's atmosphere. Philos. Mag. Ser. 4. 1863;25:200–206.

[18] Muller R.A., Muller E.A. Fugitive methane and the role of atmospheric half-life. Geoinfor Geostat: An Overview. 2017;5:3. doi:10.4172/2327-4581.1000162.

[19]https://www.epa.gov/climate-indicators/climate-change-indicators-atmospheric-concentrations-greenhouse-ases#:~:text=The%20concentration%20of%20methane%20in,agriculture%20and%20fossil%20fuel%20use.

[20]https://en.wikipedia.org/wiki/Keeling_Curve Data from Dr. Pieter Tans, NOAA/ESRL and Dr. Ralph Keeling, Scripps Institution of Oceanography.

[21]http://data.giss.nasa.gov/gistemp/graphs/.

[22]http://www.realclimate.org/index.php/archives/2004/12/how-do-we-know-that-recent-cosub2sub-increases-are-due-to-human-activities-updated/.

[23] Letcher T.M., ed. Climate Change, Observed Impacts on Planet Earth. third ed. Oxford: Elsevier; 2021 Chapters 28–33.

[24]https://www.epa.gov/gmi/importance-methane#:~:text=Methane%20is%20more%20than%2025,due%20to%20human%2Drelated%20activities.

[25]https://ourworldindata.org/energy-mix by Hannah Richie, Max Roser and Pablo Rosado.

[26]https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions.

[27]https://www.iea.org/reports/direct-air-capture.

[28]https://www.iea.org/news/global-co2-emissions-rebounded-to-their-highest-level-in-history-in-2021.

[29]https://www.globalccsinstitute.com/resources/global-status-report/.

[30]https://www.sustainablefinance.hsbc.com/carbon-transition/global-carbon-capture-and-storage-status-report-2020#:~:text=Carbon%20Capture%20and%20Storage,to%20meeting%20global%20climate%20targets.

[31] (a) https://iea.org/data-and-statistics/charts/globl-coal-consumption-by-region-2000to2021. (b) Munawer M.E. Human health and environmental impacts of coal combustion and post-combustion wastes. J. Sustain. Min. 2018;9:87–96.

[32] Letcher T.M. Future Energy: Improved, Sustainable and Clean Options for our Planet. third ed. Elsevier; 2020.

[33] Letcher T.M. Storing Energy: With Special Reference to Renewable Energy Sources. second ed. Elsevier; 2022.

[34] (a) https://www.statista.com/statistics/267358/world-installed-power-capacity/. (b) https://www.solarpowereurope.org/press-releases/world-installs-a-record-168-gw-of-solar-power-in-2021-enters-solar-terawatt-age.

[35]https://www.worldatlas.com/articles/countries-with-the-highest-share-of-solar-water-heating-collectors-global-capacity.html.

[36]https://solarthermalworld.org/news/israel-front-runner-solar-building-code-strong-impact-market/.

[37]https://renewablesnow.com/news/world-adds-936-gw-of-wind-in-2021-gwec-says-even-more-is-needed-779796/#:~:text=The%20cumulative%20global%20wind%20power,towards%20net%2Dzero%20by%202050.

[38] (a) https://orsted.com/en/media/newsroom/news/2021/12/20211220460511#:~:text=The%20world's%20biggest%20offshore%20wind%20farm%2C%20Hornsea%202%2C%20generates%20first%20power,-20.12.2021%2005&text=When%20fully%20operational%2C%20Hornsea%202's,its%20sibling%20project%20Hornsea%201. (b) https://www.hydropower.org/publications/2020-hydropower-status-report.

[39]https://www.engineeringnews.co.za/article/pioneering-1-mw-wave-energy-pilot-project-being-built-in-hermanus-2019-06-13#:~:text=Pioneering%201%20MW%20wave-energy%20pilot%20projec.

[40]https://www.marketsandmarkets.com/Market-Reports/wave-energy-market-217091216.html.

[41]https://www.power-technology.com/analysis/la-rance-learning-from-the-worlds-oldest-tidal-project/.

[42]https://www.technologyreview.com/2015/05/20/110496/why-hasnt-tidal-power-taken-off/?utm_medium=search&utm_source=google&utm_campaign=BL-ACQ-DYN&utm_content=categories&gclid=EAIaIQobChMIkYPS48u_-QIVGODtCh1cBQaiEAAYASAAEgLhofD_BwE.

[43] (a) https://www.scotsman.com/news/environment/projects-unleash-the-energy-of-orkney-3473083. (b) https://www.eia.gov/energyexplained/biomass/.

[44]https://www.statista.com/statistics/264637/world-biomass-energy-capacity/#:~:text=The%20global%20capacity%20of%20bioenergy%20plants%20totaled%20approximately%20140%20gigawatts.&text=Bioenergy%20is%20one%20of%20the,large%20part%20of%20bioenergy%20consumption.

[45]https://www.statista.com/statistics/481743/biomass-electricity-production-worldwide/.

[46] Archer R. In: Letcher T.M., ed. Future Energy: Improved, Sustainable and Clean Options for our Planet. third ed. Oxford, UK: Elsevier; 2020.

[47]https://nea.is/geothermal/.

[48]https://www.statista.com/statistics/476281/global-capacity-of-geothermal-energy/#:~:text=The%20installed%20capacity%20of%20geothermal,some%2015.6%20gigawatts%20in%20202.

[49]https://www.thinkgeoenergy.com/thinkgeoenergys-top-10-geothermal-countries-2020-installed-power-generation-capacity-mwe/.

[50]https://www.nature.com/articles/d41586-021-02338-4.

[51]https://www.ipcc.ch/report/ar6/wg2/.

[52]https://climatechange.chicago.gov/climate-change-science/future-climate-change#:~:text=Future%20changes%20are%20expected%20to,to%20reduce%20greenhouse%20gas%20emissions.

[53]https://www.wri.org/events/2022/9/using-global-forest-watch-explore-active-fires-fire-prone-regions-and-fire-trends.

[54]https://www.sciencedaily.com/releases/2022/05/220504144530.htm.

[55]https://www.wwf.org.uk/press-release/press-release-global-fires-analysis?pc=AVN014007.

[56] (a) https://www.un.org/development/desa/undesavoice/highlights/2020/03/48819.html. (b) https://www.woodwellclimate.org/climate-change-food-security-crop-failures/.

[57] Holt-Giménez E., et al. We already grow enough food for 10 billion people … and still can't end hunger. J. Sustain. Agricult. 2012;36(6):595–598. doi:10.1080/10440046.2012.695331.

[58]https://reliefweb.int/report/world/drought-numbers-2022-restoration-readiness-and-resilience.

[59]https://www.metoffice.gov.uk/research/climate/understanding-climate/uk-and-global-extreme-events-heavy-rainfall-and-floods.

[60]https://royalsociety.org/topics-policy/projects/climate-change-evidence-causes/question-14/#:~:text=Long%2Dterm%20measurements%20of%20tide,(0.14%20inches%20per%20year).

[61]https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level.

[62]https://www.un.org/en/climatechange/climate-adaptation?gclid=EAIaIQobChMIpsagvJDC-QIVxOvtCh3hRA3GEAAYAyAAEgLWHvD_BwEhttps://www.un.org/en/climatechange/climate-adaptation?gclid=EAIaIQobChMIpsagvJDC-QIVxOvtCh3hRA3GEAAYAyAAEgLWHvD_BwE.

[63]https://www.bmj.com/communicable-diseases.

[64] Gardiner S.M., Hartzell-Nichols L. Ethics and global climate change. Nature Educ. Knowl. 2012;3(10):5.

[65]https://www.dw.com/en/how-climate-change-paved-the-way-to-war-in-syria/a-56711650.

[66]https://www2.deloitte.com/us/en/pages/financial-services/articles/insurance-companies-climate-change-risk.html.

[67]https://www.unepfi.org/psi/issues-paper-on-climate-change-risks-to-the-insurance-sector/.

[68]https://www.migrationpolicy.org/topics/climate-change?gclid=EAIaIQobChMIifaWpYPE-QIVhO7tCh2Jlw_LEAAYAyAAEgLJdPD_BwE.

[69]https://www.un.org/en/chronicle/article/climate-change-poses-threat-our-oceans.

[70] Feely R.A., Doney S.C., Cooley S.R. Ocean acidification: present conditions and future changes in a high-CO2 world. Oceanography. 2009;22(4):36–47.

Chapter 2 An engineer's assessment on adapting to global warming and climate change

Daniel Alan Vallero    Pratt School of Engineering, Duke University, Durham, NC, United States

Abstract

Engineers’ major strength is applying scientific knowledge to identify problems and optimize solutions to their client's needs. The engineer's principal client is the public. The most pressing of society's challenges are protecting public health and the environment. Among the key aspects of this protection are ways to address and prevent problems associated with climate change. To this end, engineers must innovatively apply the physical and biological sciences to control and manage the generation and release of greenhouse gases. This is best achieved through systems approaches that successfully apply thermodynamics and fluid dynamics within proper social, economic, and cultural contexts and effectively communicating solutions to the scientific community and the public.

Keywords

Environmental engineering; Climate change adaptation; Carbon sequestration; Geoengineering; Systems thinking; Root cause analysis; Life cycle assessment

1 Introduction

Engineers are aptly proud to be called problem solvers, but they do more than that. In fact, the best, but too often unappreciated, role is as problem preventers. They are also knowledge prospectors who can identify previously unnoticed opportunities to maximize benefits. These characteristics are the right mix to address the seemingly intractable problems associated with changes in climate. Planetary-scale problems that may or may not occur must often be met with adaptive solutions [1]. In addition to their strengths in the physical sciences, engineers must ensure that their proposed actions be feasible. Feasibility goes beyond engineering reliability. An action must also be economically and socially feasible and accepted by the policy makers and the public.

2 Application of the physical, natural, and social sciences

Climate change challenges are being addressed by every engineering profession. Arguably, the civil engineering and its subdiscipline, environmental engineering, have been most directly tagged with innovative ways to control and treat all types of pollutants, especially air pollutants that include the greenhouse gases (GHGs). However, chemical and petroleum engineers are constantly working to improve chemical reactor systems to decrease GHG emissions [2–4] and to find and use safer chemicals to meet the needs for refrigeration, transportation, and other societal demands [5,6]. Structural engineers pioneer systems with less carbon footprints [7,8]. Mechanical engineers are designing more energy-efficient engines, turbines, and green technologies like electric vehicles (EVs) and windmills [9–11]. Material sciences have found new metallurgical applications for lighter and more environmentally friendly manufacturing [7,12–15]. Agricultural and biosystems engineers address needs to adapt crops and natural habitats to droughts and other climate-induced stresses [16,17]. Biomedical engineers are constantly looking for ways for the human body to address environmental insults, including those imposed by a changing climate [18]. Software engineers are finding new data mining and informatic tools to support all of these efforts [19–24]. All of these are direct or indirect applications of the physical sciences. Engineers must be part of any team intent on solving the indirect and social adaptation challenges associated with climate change [1]. Among the areas where engineering knowledge helps to optimize among alternative actions and decisions are:

•to provide goods and services to migrating populations;

•to prevent and address the opportunistic entry induced by habitat changes of disease vectors like vermin, mosquitos, and other insects to hitherto uninfected areas;

•to address biome shifts and their effects on agriculture, including planting, harvest, transportation, and storage; and

•to improve designs to meet challenges to infrastructure, for example, flood control, water supply, wastewater treatment, roads, railway, and ports [1].

The individual engineer is held to standards of performance to respond not only to a particular design but to the public, which incrementally supports the challenges of climate change [25–28]. However, macro-scale issues like climate change also need a top-down strategy by the engineering profession [29–32]. This is evident in the American Society of Civil Engineering's Grand Challenges. Some of these challenges are directly or indirectly aimed at stemming adverse effects from climate change that are expected to worsen without an assertive engineering role to meet the challenge [33,34] Notably, engineers need to apply knowledge and expertise related to the globe's biogeochemical cycles [35–37].

Pollution control technologies are a key area that must advance. Air pollution controls remove and treat emissions, especially products of incomplete combustion. Incomplete combustion represents inefficiency. As such, a common engineering measure of combustion efficiency is to completely oxidize organic compounds to produce carbon dioxide (CO2) and water. Ironically, both are GHGs. Engineers must also design systems to remove and store CO2 and other GHGs, that is, sequestration. Of course, the most effective role of engineers is to help to prevent the formation of GHGs in the first place. They must continue to adapt and innovate processes to approach zero GHG emissions, that is to deploy green engineering. This is the design, commercialization, and use of processes and products that are feasible and economical, while lowering the amount of pollution generated by source and minimizing the health risks and reducing environmental stress [38]. Thus pollution control technologies must be part of a comprehensive, systematic engineering strategy [39,40].

3 Systems thinking

Engineers must consider the entire life cycle of processes that result in climate change and appropriately scale corrective actions to the problems presented. Climate change is global in scale, so outcomes associated with these changes must also be global. Incremental actions within the systematic approach are needed to achieve global outcomes, however. The smaller-scale decisions and actions, such as an individual's decision to purchase a product with fewer or less potent GHG emissions over the product's life cycle than a competing product, combine to affect larger scales. This also implies that an action that is preferable during one stage of the life cycle may not be the best alternative when considering the entire life cycle. The end-of-product-life of a plastic cup A may emit 20% less CO2 compared to cup B after disposal in a landfill. However, if during the manufacturing stage, cup A releases twice as much CO2 than in producing cup B, the math works in favor of cup B. Furthermore, the systems view requires a multifactorial perspective, and alternatives assessment seldom involves a single pollutant or process. Regarding climate change, numerous GHGs come into play during various stages of a product's life cycle. If, during the manufacturing of one of the cups mentioned above, large amounts of nitrous oxide (N2O) are emitted, buying that cup would not be preferable, although emissions after product uses would be less. Thus, the saying think globally, but act locally applies not only to spatial scale but to life cycles [41,42].

4 Root causes

Carbon cycles through the Earth with the biogeochemical cycles of other substances, especially N, S, and other nutrients. Carbon dioxide is the product of abiotic and biological reactions. A principal abiotic reaction is the combustion of organic compounds, whereas CO2 is respired following metabolism. Oxidation of carbon compounds generates CO2. At the other end of the redox is reduction. The major GHG in the carbon cycle resulting from reduction is methane (CH4), which is a product of anaerobic decomposition.

Another class of carbon-containing GHGs is the halocarbon group, which is also a culprit in the destruction of the stratospheric ozone layer [43,44]. CFC-11 and CFC-12 are no longer manufactured, and this is part of the reason the ozone layer is recovering