Managing the Climate Crisis: Designing and Building for Floods, Heat, Drought, and Wildfire

By Jonathan Barnett and Matthijs Bouw

The climate, which had been relatively stable for centuries, is well into a new and dangerous phase. In 2020 there were 22 weather and climate disasters in the United States, which resulted in 262 deaths.  Each disaster cost more than a billion dollars to repair. This dangerous trend is continuing with unprecedented heat waves, extended drought, extraordinary wildfire seasons, torrential downpours, and increased coastal and river flooding. Reducing the causes of the changing climate is the urgent global priority, but the country will be living with worsening climate disasters at least until midcentury because of greenhouse emissions already in the atmosphere. How to deal with the changing climate is an urgent national security problem affecting almost everyone.  

In Managing the Climate Crisis, design and planning experts Jonathan Barnett and Matthijs Bouw take a practical approach to addressing the inevitable and growing threats from the climate crisis using constructed and nature-based design and engineering and ordinary government programs. They discuss adaptation and preventive measures and illustrate their implementation for seven climate-related threats: flooding along coastlines, river flooding, flash floods from extreme rain events, drought, wildfire, long periods of high heat, and food shortages.

The policies and investments needed to protect lives and property are affordable if they begin now, and are planned and budgeted over the next 30 years. Preventive actions can also be a tremendous opportunity, not only to create jobs, but also to remake cities and landscapes to be better for everyone. Flood defenses can be incorporated into new waterfront parks. The green designs needed to control flash floods can also help shield communities from excessive heat. Combating wildfires can produce healthier forests and generate creative designs for low-ignition landscapes and more fire-resistant buildings. Capturing rainwater can make cities respond to severe weather more naturally, while conserving farmland from erosion and encouraging roof-top greenhouses can safeguard food supplies.

Managing the Climate Crisis is a practical guide to managing the immediate threats from a changing climate while improving the way we live.

• Language: English
• Publisher: Island Press
• Release date: Jul 14, 2022
• ISBN: 9781642832013

Book preview

About Island Press

Since 1984, the nonprofit organization Island Press has been stimulating, shaping, and communicating ideas that are essential for solving environmental problems worldwide. With more than 1,000 titles in print and some 30 new releases each year, we are the nation’s leading publisher on environmental issues. We identify innovative thinkers and emerging trends in the environmental field. We work with world-renowned experts and authors to develop cross-disciplinary solutions to environmental challenges.

Island Press designs and executes educational campaigns, in conjunction with our authors, to communicate their critical messages in print, in person, and online using the latest technologies, innovative programs, and the media. Our goal is to reach targeted audiences—scientists, policy makers, environmental advocates, urban planners, the media, and concerned citizens—with information that can be used to create the framework for long-term ecological health and human well-being.

Island Press gratefully acknowledges major support from The Bobolink Foundation, Caldera Foundation, The Curtis and Edith Munson Foundation, The Forrest C. and Frances H. Lattner Foundation, The JPB Foundation, The Kresge Foundation, The Summit Charitable Foundation, Inc., and many other generous organizations and individuals.

The opinions expressed in this book are those of the author(s) and do not necessarily reflect the views of our supporters.

Island Press’s mission is to provide the best ideas and information to those seeking to understand and protect the environment and create solutions to its complex problems. Click here to get our newsletter for the latest news on authors, events, and free book giveaways.

Managing the Climate Crisis

DESIGNING AND BUILDING FOR FLOODS, HEAT, DROUGHT, AND WILDFIRE

Jonathan Barnett and Matthijs Bouw

Washington

Covelo

© 2022 Jonathan Barnett and Matthijs Bouw

All rights reserved under International and Pan-American Copyright Conventions. No part of this book may be reproduced in any form or by any means without permission in writing from the publisher: Island Press, 2000 M Street, NW, Suite 480-B, Washington, DC 20036-3319.

Library of Congress Control Number: 2021947902

All Island Press books are printed on environmentally responsible materials.

Manufactured in the United States of America

10 9 8 7 6 5 4 3 2 1

Keywords: American Society of Civil Engineers (ASCE), climate action plan, coastal flooding, ecosystem benefits, farmland preservation, Federal Emergency Management Agency (FEMA), floodplain, floodwall, food scarcity, freshwater scarcity, global warming, green-blue solutions, green infrastructure, heat wave, levee, managed retreat, nature-based solutions, resilience planning, riverine flooding, sea level rise, storm surge, stormwater management, US Army Corps of Engineers, wildfire, zoning

ISBN-13: 978-1-64283-201-3 (electronic)

Contents

PART I: UNDERSTANDING THE CLIMATE CRISIS

Chapter 1: The Climate Crisis: A National Security Problem

Chapter 2: The Causes and Dangers of a Warming Climate

PART II: MANAGING CLIMATE THREATS

Chapter 3: Flooding from Sea Level Rise and Storm Surges

Chapter 4: Flooding along Rivers

Chapter 5: Flooding from Extreme Storm Events

Chapter 6: Life-Threatening Heat

Chapter 7: Shortages of Fresh Water

Chapter 8: Wildfire

Chapter 9: Food Shortages

PART III: LOOKING AHEAD

Chapter 10: Recent Progress in Managing Climate Threats

Chapter 11: Costs and Benefits of Managing Climate Threats

Chapter 12: How Managing the Climate Crisis Can Transform the United States

Acknowledgments

Illustration Credits

Notes

Index

About the Authors

PART I

UNDERSTANDING THE CLIMATE CRISIS

CHAPTER 1

The Climate Crisis: A National Security Problem

The climate, which had been relatively stable for centuries, is well into a new and dangerous phase. In 2020, 448 deaths in the United States were caused by the weather.¹ Among these deaths, 262 were the result of twenty-two weather and climate disasters, each of which caused more than $1 billion in damage. They included flooding and wind damage from thirteen severe storms, seven hurricanes, and a series of horrific West Coast wildfires. (See figure 1-1.) The toll from major climate-related disasters has been increasing steadily over the past decades.² Events since the 2020 statistics were compiled show the dangerous trend continuing: unprecedented heat waves, extended drought in the West and Southwest, extraordinary wildfire seasons fueled by heat and drought, torrential downpours, increased coastal and river flooding.

Gases added to the atmosphere from an industrialized world are preventing more and more heat from being radiated back into space, causing global temperatures to rise and destabilizing the weather. And what is already a bad situation will become far worse. The Intergovernmental Panel on Climate Change (IPCC), in its explanation of the physical science basis for its Sixth Assessment Report, noted that global temperatures are already higher than they have been at any time since an interglacial warm period 6,500 years ago and that the only previous warmer period occurred 125,000 years ago. The IPCC used its strongest language to date to emphasize that human influence has been warming the climate at an unprecedented rate and that the world is on track toward dangerously higher temperatures unless far-reaching changes take place right away. The report puts forward five possible scenarios for future concentrations of greenhouse gases in the atmosphere, from optimistic to a worst case. The most optimistic projection, that the world soon makes drastic reductions in the emissions of greenhouse gases, still shows greenhouse gas concentrations rising until midcentury, when they level off and then gradually decline. The worst case—nothing effective is done to reduce emissions—shows the concentration of greenhouse gases rising sharply by 2050 and going rapidly up from there. The intermediate scenarios show rising greenhouse gas concentrations continuing past the middle of the century. Because of greenhouse gas emissions already in the atmosphere, the report concludes that global surface temperature will continue to increase until at least the mid-century under all emissions scenarios considered.³

Image: Figure 1-1: This map, adapted from one published by the National Oceanic and Atmospheric Administration (NOAA), shows the approximate location of each of twenty-two weather and climate disasters in 2020 in which the damage was more than $1 billion. The wildfire symbol includes fires in California, Oregon, and Washington. The drought symbol stands for heat waves and drought in the central and western states.

Figure 1-1: This map, adapted from one published by the National Oceanic and Atmospheric Administration (NOAA), shows the approximate location of each of twenty-two weather and climate disasters in 2020 in which the damage was more than $1 billion. The wildfire symbol includes fires in California, Oregon, and Washington. The drought symbol stands for heat waves and drought in the central and western states.

One possible path for reducing greenhouse gas emissions in time to meet the most optimistic IPCC scenario was laid out in a 2017 book edited by Paul Hawken, Drawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming. A second version, The Drawdown Review, was issued by Project Drawdown, an organization formed to promote these proposals. Drawdown is the point where greenhouse gases in the atmosphere are brought under control and concentrations begin to decrease.⁴

Reaching drawdown is the most urgent issue facing the entire planet. It will require unprecedented international cooperation. But while these negotiations take place, and while every country takes steps to meet its own share of the necessary changes, the United States must also confront and deal with the certainty of increasing dangers from the changing climate for at least the next thirty years. In addition to risks to life and property, there are risks for the entire system of governmental and private finance. Costs for fighting floods and wildfires go up every year, and losses from crop failures are increasing. Extreme heat and unexpectedly cold weather are putting stress on infrastructure not designed for such temperatures. Insurance rates are going up, and government subsidies for insurance are running out. As people migrate away from vulnerable places, exposure to risk reduces property values for those remaining, causing economic uncertainty and anguish to families and reducing the property tax base, which in turn will have a negative effect on bond ratings. The viability of whole cities and towns could be at risk. Falling property values also undermine the stability of mortgages held by banks or incorporated in securities. Major property investors will withdraw money from places where the future seems uncertain. These factors could cause a national financial crisis even before the worst of the physical dangers begin.⁵

The urgency of reducing greenhouse gas emissions should not distract us from the equally urgent need to protect the country from what will be happening until emissions can be controlled.

This book is about what we can do to manage these immediate challenges. The crisis is global, but dealing with its effects successfully depends on local conditions, which is why we focus on prototypical issues in the United States, usually the contiguous forty-eight states, adding the necessary information about Alaska, Hawaii, and the territories when it is available.

Decisions about development and construction should be made with climate considerations in mind, beginning immediately. Decisions about development that do not consider the effects of inevitable changes in the climate make the eventual costs of adaptation higher and the adjustments that people will have to make more difficult. Our research has shown us that timely preventive actions are well within the country’s financial capacity if they are planned and budgeted in advance and implemented incrementally as they are needed. Managing the climate crisis will be far less expensive than recovering from recurring disasters and the physical and financial risks of continued inaction.

The expenditures needed to keep people and property safe will create tens of thousands of well-paying jobs as well as tremendous opportunities to correct mistakes in the way the country has developed, making our cities, suburbs, and rural areas safer, more inclusive, and more livable in the next three decades and onward, if global emissions reductions can be achieved.

The Climate Crisis Now and by Midcentury

The IPCC’s Sixth Assessment Report documents seven consequences of the increase in greenhouse gases that has occurred since 1950.⁶ Every part of the United States will feel some of these effects, and many places are experiencing them already. Hurricanes will be more intense and possibly more frequent. Storm surges and regular coastal flooding will increase. There will be more periods of heavy rain or snow. The hottest days will be hotter, and there will be more of them. Heat waves will be longer and more intense, and winters will be warmer with fewer cold days. Periods of drought will be longer and more severe.

Danger from Floods: According to a recent report by the First Street Foundation, right now 3.6 million properties—2 percent of all properties in the continental United States—are at immediate risk of flooding, a 20 percent chance every year. A much larger group is in the current 100-year floodplain (meaning a risk of 1 percent each year): 14.6 million properties, 10.3 percent of all properties. The 500-year floodplain extends the danger of flooding to 21.8 million properties, 15.4 percent of all properties.

The First Street Foundation is a nonprofit organization based in Brooklyn, New York, that does research to determine the degree of danger from flooding for properties across the United States. First Street considers more factors than the Federal Emergency Management Agency (FEMA), so its figures for properties at risk from floods are larger. First Street also makes estimates of future flooding, whereas FEMA figures are all based on previous floods.

The First Street numbers include all three major causes of flooding: coastal flooding from higher tides or storm surges, flooding along rivers, and flooding inland, away from major streams, from torrential downpours.

Looking forward to 2050, First Street predicts that the number of properties at risk from flooding will increase moderately, to a total of 23.5 million properties, but many of these properties are much more likely to flood than they are now. First Street defines five categories of risk by midcentury: extreme (4.8 million properties), severe (2.8 million), major (7.4 million), moderate (7.2 million), and minor (1.3 million). These numbers add up to a prediction that 16.5% of individual homes and properties in the U.S. are at some risk of flooding over the next 30 years. Out of those at risk, 64.1% are at major to extreme risk.⁷

Danger from Extreme Heat: Killer Heat in the United States: Climate Choices and the Future of Dangerously Hot Days is the title of a report published in 2019 by the Union of Concerned Scientists. According to the report, until recently only three cities with populations of fifty thousand or more in the contiguous United States have experienced thirty or more days per year with a heat index above 105°F, temperatures at which continued exposure can be dangerous for human life. Even with some effective action by midcentury to reduce global emissions, more than 80 such cities would experience thirty or more days of dangerous heat conditions by midcentury. And with no effective action globally, more than 150 cities would. (See figures 1-2a and 1-2b.)

By midcentury, some areas could even experience days above 127°F, which is the current upper limit of the National Weather Service’s heat index scale. The increased humidity contained in warmer air can make such heat even more dangerous. The number of people suffering through thirty or more days with temperatures above 90°F, which is already expected during the summer in some places, will more than double, even with reductions in greenhouse gas emissions.⁸

Image: Figures 1-2a and 1-2b: The large dots on these maps, adapted from a publication by the Union of Concerned Scientists, show cities in 2050 experiencing a heat index of greater than 105°F for more than thirty days per year under two scenarios: figure 1.2a if no effective action is taken to reduce greenhouse gas emissions, and figure 1.2b if some reductions have taken place. The three circles on the southwestern coast denote cities already experiencing more than thirty days of extreme heat per year. The smaller dots are cities of more than fifty thousand people that will also experience some days of heat over 105°F. According to the Union of Concerned Scientists’ report, with no effective action to reduce greenhouse gas emissions, more than 150 urban areas will experience extended periods of extreme heat by midcentury; with some reductions in emissions, the number will still be more than 80.Image: Figures 1-2a and 1-2b: The large dots on these maps, adapted from a publication by the Union of Concerned Scientists, show cities in 2050 experiencing a heat index of greater than 105°F for more than thirty days per year under two scenarios: figure 1.2a if no effective action is taken to reduce greenhouse gas emissions, and figure 1.2b if some reductions have taken place. The three circles on the southwestern coast denote cities already experiencing more than thirty days of extreme heat per year. The smaller dots are cities of more than fifty thousand people that will also experience some days of heat over 105°F. According to the Union of Concerned Scientists’ report, with no effective action to reduce greenhouse gas emissions, more than 150 urban areas will experience extended periods of extreme heat by midcentury; with some reductions in emissions, the number will still be more than 80.

Figures 1-2a and 1-2b: The large dots on these maps, adapted from a publication by the Union of Concerned Scientists, show cities in 2050 experiencing a heat index of greater than 105°F for more than thirty days per year under two scenarios: figure 1.2a if no effective action is taken to reduce greenhouse gas emissions, and figure 1.2b if some reductions have taken place. The three circles on the southwestern coast denote cities already experiencing more than thirty days of extreme heat per year. The smaller dots are cities of more than fifty thousand people that will also experience some days of heat over 105°F. According to the Union of Concerned Scientists’ report, with no effective action to reduce greenhouse gas emissions, more than 150 urban areas will experience extended periods of extreme heat by midcentury; with some reductions in emissions, the number will still be more than 80.

Danger of Running Out of Fresh Water: A changing climate is producing a challenging combination of longer and more intense droughts, plus increased flooding in some parts of the country, including flooding from torrential storms, which are expected to become more frequent. People in drought-prone areas are learning to use somewhat less water, but the population is also growing in many of these places, which adds complexity to making predictions about future water demand. In addition, there is a wide range of possible climate change scenarios.

An article in the journal Earth’s Future by Thomas C. Brown, Vinod Mahat, and Jorge A. Ramirez addresses all these complexities. They measured stress on water supplies by looking at the availability of water according to the drainage basins of rivers and concluded that changes in available fresh water vary significantly depending on the water basin. Using an average of fourteen potential climate change scenarios from the past to the middle of this century, they found that 145 basins showed decreases in freshwater availability and 59 showed increases, with the most severe decreases occurring in the Southwest, the middle to southern Great Plains, and Florida, and the greatest increases occurring in the larger Northwest, Great Basin, and California. Figure 1-3 shows the percentage change in water availability between 2010 and midcentury, using a mean of fourteen potential climate change scenarios. Projected changes in demand also vary across the different river basins, increasing in most but decreasing slightly in a few western basins, which have already had to respond to water shortages.⁹

Image: Figure 1-3: This map is adapted from information in an article by Thomas C. Brown, Vinod Mahat, and Jorge A. Ramirez in the journal Earth’s Future that concludes that changes in available fresh water vary significantly depending on the watershed. Using an average of fourteen potential climate change scenarios from the past to the middle of this century, they found that 145 basins showed decreases in availability and 59 showed increases. On this map, the darkest areas have the most plentiful water supplies and the lightest areas are places of severe water shortage.

Figure 1-3: This map is adapted from information in an article by Thomas C. Brown, Vinod Mahat, and Jorge A. Ramirez in the journal Earth’s Future that concludes that changes in available fresh water vary significantly depending on the watershed. Using an average of fourteen potential climate change scenarios from the past to the middle of this century, they found that 145 basins showed decreases in availability and 59 showed increases. On this map, the darkest areas have the most plentiful water supplies and the lightest areas are places of severe water shortage.

Dangers from Wildfires: According to a recent article in the Proceedings of the National Academy of Sciences, the wildland-urban interface (WUI)—the land and buildings located close to or within forest or other wildland areas—is the location for approximately one in every three houses and makes up 10 percent of all land area in the continental United States. Between 1990 and 2010, the number of houses considered to be close to or part of wildland grew from 30.8 million to 43.4 million, and developed land area in the WUI grew by one-third.¹⁰ When analysis of the data from the 2020 census is complete, it is likely to show that rapid growth continues close to wildland areas. Building near wildland raises the risk of fires because human activities start most of them, and being so close raises the risk to inhabitants when a fire starts.

Horrifying wildfires have recently afflicted communities mostly in the western United States, but the WUI extends across the entire country. Most people who live in close proximity to these other wildlands are not aware that they may be in danger because the risk of fire has been low. But the warming climate is bringing longer periods of very hot weather, extended droughts, and changes in the growing season, which will bring risks from wildfire to many additional parts of the United States by midcentury.

Problems Maintaining the Food Supply: There are already severe food shortages in many places in the world from a combination of rising populations and reductions in farm productivity because of a changing climate. When people are unable to obtain food and other necessities, their only resort is to move. Climate refugees from Central America are migrating to the United States’ border with Mexico, and there are already major movements of population in Africa and the Middle East. The United States is fortunate to have large amounts of fertile land and a good climate for growing food. But as the growing seasons change, crops can become less well adapted to the places where they are flourishing now. Although growing seasons farther north may become more suitable for these crops, the right combination of soils and water resources may not be available. The United States has permitted massive erosion of soils by wind and water, has endangered future productivity by overuse of chemical fertilizers, and continues to permit suburban growth to pave over agricultural land. Increasing stress on crops from floods, heat waves, and droughts means the country cannot be complacent about the future of the food supply.

The Need for Immediate Action

In this book, we outline the physical measures and the policies that will be needed to manage the changing climate between now and the middle of the century so that people remain safe and the economy is not unnecessarily disrupted. We do this by describing actions that can be incorporated into normal decision-making, although sometimes they will require new funding sources. Often, these measures have already been implemented somewhere but need to be replicated on a much larger scale.

Our recommendations follow principles that you will see throughout our book.

Base All Climate-Related Actions on the Best Available Science: Climate change is different from place to place, so all actions to manage climate change should be based on the best possible scientific predictions for what to expect in each locality.

Restore and Enhance Natural Systems: Working with—not against—natural forces will almost always prove to be the most effective and economical way of managing the rapidly changing climate, especially for flood protection, wildland management, heating and cooling of buildings, and agriculture.

Make a Public Process Part of All Government Decisions about Climate Management: Managing the climate crisis will require many difficult decisions. Everyone affected should know what the issues are, take part in decisions about what is being proposed, and feel they have been treated as fairly as possible. Comment periods after plans have been prepared are not a substitute for public participation in decisions.

Lay Out Adaptation Pathways for Climate Management Decisions: Dealing with future conditions that are only partly predictable requires flexibility. After a phase of adaptation is complete, there may still need to be decisions about what to do next.

Make Future Climate Considerations Part of All Codes and Regulations: Zoning and subdivision regulations shape all new development and also control changes to what exists already. Geographic information systems (GIS) technology can inform decision-making by mapping environmental factors and relating them to potential zoning changes as overlays. Building codes establish minimum requirements for all inhabited structures and set standards for protection from fires and—in some places—earthquakes, but few codes have extended comparable safety protections to risks caused by floods, by wildfires that engulf whole areas, by heat waves, or by freshwater shortages.

Make Future Climate Factors Part of All Infrastructure Decisions: Much of the infrastructure in the United States needs to be repaired or even rebuilt. All expenditures for infrastructure should be made with an understanding of future resilience from climate threats. Railroad rights-of-way often follow shorelines because the land is relatively level and the grade changes gradually. Highways often follow shorelines for similar reasons. Utilities were designed for worst-case storm conditions that might now be surpassed. Intakes for water systems and outfalls for sewers were determined at a time when water levels were relatively stable. These critical structures may need to be rebuilt or relocated.

Begin Planning and Building the Protections Needed Now and by Midcentury: Rising sea levels and more extensive flooding are making climate disasters more frequent and extending the places affected. Unprecedented flooding is already taking place. Densely populated regions will need to have additional protections in the form of enhanced natural barriers, engineered seawalls, and combinations of both. These protections will be expensive, but the expense will be justified by the safety they can provide for residents and businesses. The costs can be managed if the necessary work starts now and is done incrementally up to what will be needed by midcentury.

Stop Building in the Wrong Places: It should be obvious, but apparently it is not, that people should stop building in places that are close to—or within—wildland that is in danger of burning or places where recurring flood conditions are already happening and no additional flood protection is anticipated. In the past, disasters might have been infrequent, and insurance policies were available if things went wrong. In the future, insurance—even government-backed insurance—will stop covering properties that are clearly liable to be damaged by recurring climate disasters. But local governments should not wait to have lack of insurance coverage force decisions; they need to study the potential for future change and plan for it. As mentioned earlier, buildings made uninhabitable by a changing climate mean less tax revenue, which could affect bond ratings, as does the risk to municipal infrastructure.

Start Building in the Right Places: Places with a more stable climate future, both locally and nationally, should be identified as opportunity zones for future development, but based on policies that protect existing residences and businesses.

Plan For and Fund Equitable Relocations: Inevitably, there will be places where enhanced protections from present and future climate disasters are either not feasible or not economic. But identifying these places using only engineering and financial analysis will create huge inequities. Some of society’s most vulnerable people and businesses are likely to occupy the most vulnerable real estate, often as the result of deliberate exclusionary policies. These people might lack the resources to move. And even adequate financial resources will not protect people from wrenching decisions about where to move and when to sever their connection to a place where they may have lived for a long time. Yet state and local governments need to identify locations where future human occupation is questionable, using the best scientific information available. Feasibility studies can show whether physical protection is possible and, if not, what the relocation options are. This process has to be accompanied by extensive involvement of the people who will be affected. No one wants to hear that their property investment may lose its value and that their life will be disrupted. The politics of initiating such discussions are daunting. But it is better to begin while options are available and not wait for the aftermath of the next disaster. Governments should recognize from the beginning that there will be high costs either for protection or for buying out the people and businesses that have to move. These costs will be more manageable if they are incurred incrementally, before the worst-case scenario becomes a reality.

Make Climate Management an Opportunity for a Better Future: The investments required to manage a changing climate are also an opportunity for reimagining our communities to be more inclusive, more livable, and more in harmony with natural processes.

Toward Current and Future Climate Management

We have written this book as a summary and guide to managing the way the climate crisis will affect the built environment between now and mid-century, drawing on our extensive experience in urban and environmental design and the best additional information we could find. Making decisions about managing the effects of a changing climate is going to be a very difficult process with few precedents. It will require substantial amounts of money—although nowhere near as much as the costs of failing to act. It will also force difficult choices on a high proportion of the US population. Making these choices as equitable as possible, and giving everyone acceptable options, will take a long time and a great deal of public discussion.

We are hoping we can make a useful contribution to the work of managing climate change, and we have organized the book to make this complicated subject as accessible as possible.

Chapter 2 is a brief introduction to the natural forces that global warming has set in motion and that are reshaping the climate.

Chapters 3–9 describe the major climate threats: flooding along coasts, along rivers, and from heavy rains; heat waves; drought and freshwater shortages; wildfire; and food shortages. We describe the climate forces at work, what is being done to meet these threats today, and what actions will be needed to manage the effects of climate change up to the middle of the century.

Chapters 10–12 outline the public policy decisions that will be needed—particularly so that the burdens of adaptation are shared equitably. We describe mobilization already in progress to manage climate change. We then review the costs and benefits of climate management using examples of cost estimates from projects already begun. We show in chapter 11 that the costs are manageable if actions begin right away and keep pace with the threats from a changing climate that will be taking place by midcentury. In conclusion, we describe how to implement the actions required by the climate crisis and the ways they can also improve urban and rural areas and undo many of the mistakes made in previous development.

We emphasize that managing what is already inevitable is not a substitute for making worldwide reductions in the ways that human activities are warming the atmosphere. Understanding the difficulties and costs of adaptation is a powerful argument for immediate, effective actions to reduce unfavorable climate trends. The window for making meaningful change is closing. If big improvements in controlling greenhouse gas emissions are not started soon and completed by midcentury, the future will be much more challenging. The longer the