RIGHT HERE, RIGHT NOW

!!!!!!!!! !!!!!!!!!A Communications Guide !!!!!!!!!to Climate Change Impacts Right Here, Right Now

A Communicaons Guide to Climate Change Impacts Cover photo: Reeve Jolliffe. Traffic and street lights in New York City disabled by Hurricane Sandy.

Version 1.1

For informaon contact:

Hunter Cung Director of Strategic Communicaons Climate Nexus +1 415-420-7498 hcu[email protected]

This work is licensed under the Creave Commons Aribuon-NoDerivs 3.0 Unported License.

New York, NY Jan. 2013 Table of Contents

Execuve Summary ...... 5

Communicaon Guidelines ...... 10

Signatures of Climate Change ...... 14

Extreme Weather ...... 14 Season Creep ...... 21 Arcc Sea Ice ...... 22 Ice Sheets and Glaciers ...... 23 Sea Level Rise ...... 25 Ocean Acidificaon ...... 26 Human Health ...... 27 Society and Systems ...... 29 Food Price and Supply ...... 30

“How Do We Know?” ...... 31

Example Language ...... 32

Acknowledgements ...... 33

Endnotes ...... 34

Sources ...... 37 Execuve Summary

We are no longer discussing the threat of The science of fingerprinng has developed climate change. We are living with the reality significantly in the last several years, and we of it, right here and right now. Today the can connect the dots with confidence. The impact of climate disrupon in the United news media are increasingly recognizing the States is clear, costly and widespread.1,2,3,4 links to climate change and the massive Importantly, these changes are teachable scienfic evidence supporng them. And moments that can help galvanize public will perhaps most importantly, a majority of for climate protecon. Americans now connect the dots themselves and are changing their atudes as a result. The fingerprint of global warming is found on Taken together, these trends make climate disasters ranging from raging wildfires and change impacts, right here and right now, a flooded coastlines to extreme heat waves powerful focus in the fight for climate and the growing threat of asthma.5 Weather protecon. catastrophes have tripled in North America over the last 30 years, incurring over $1 The links between climate change on one trillion in damages.6,7 Climate disrupon has hand and damage and disaster on the other driven up food prices,8 are complex and can be tricky to talk about increased the risk of in the sound-bite vernacular of mainstream West Nile outbreaks media. Helping Americans understand the across the U.S.,9 link between climate change and disaster and helped fuel requires a well-craed and disciplined wildfires that approach. As the public increasingly caused over $1 recognizes the changing weather they are billion in damages in living through, the broader changes to other 2012.10 Our seas are facets of society must also be recognized and now 30 percent more understood. This presents challenges to acidic due to the sciensts, elected leaders, health care carbon polluon providers, policymakers and communicators. taken up by the The threats are myriad and complex, but oceans.11 Global warming they are rooted in climate disrupon and drives up sea levels, increasing unfold within the context of the the reach of storm surge12 and dramacally communies, governments and economies amplifying disasters such as Superstorm that must adapt to such changes. By their Sandy.13 Half of the summer sea ice in the nature, disasters can open eyes and drive Arcc has been lost due to warming,14 a polical will. To help meet this change that has altered global weather communicaon challenge, this guide offers paerns, and brought harsh winter storms tools and strategies for making current south to the United States.15 climate change impacts clear and understandable.

5 Impacts the threat. Weather is the foundaon for many of the impacts happening here and As science has long predicted, climate now so for the full scope of the problem to change is bringing damage and disrupon to be seen clearly, the links to disrupon must ecosystems, infrastructure and society across be made explicit. the United States: Seasons: Season creep has been increasing Infrastructure: Through heat waves that for years. Although it poses immediate risk to cripple ulies’ cooling systems, western farmers and food supply, the impacts extend fires that destroy neighborhoods, storm to damaged ecosystems and other surges that devastate public transportaon repercussions that are only now being systems and road networks, and much more, grasped. Bark beetle infestaons across the climate disrupon is damaging the physical West that decimated old-growth forests are foundaons of modern society. The range of one vivid example, but others, such as a ski systems threatened by climate disrupon industry crippled by low snow pack, illustrate encompasses transit and transportaon, the how climate change threatens the businesses electric grid, the public health network, and acvies that anchor the U.S. economy. emergency response and water and sewage systems. Geophysical changes: The unprecedented changes to the Arcc sea ice, Greenland ice Food: Droughts, heat waves and extreme sheet and glaciers in Antarcca and beyond precipitaon are impacng crop producon, pose a series of threats that cross boundaries leading to spikes in food prices and of all other impacts. These changes help disrupons in food supply. Recent drought in drive sea level rise, play crical roles in global the southern Plains accounts for losses in the weather formaon, are fundamental to billions. Damage to transportaon systems is water supply and crop producon, and are a another source of disrupon for food pivotal force in determining ocean currents. supplies, as reflected in the challenges for The links between these ongoing and record- grain producon and distribuon posed by breaking changes and our daily lives must be the recent record-low water levels in the made as explicit as possible, even as science Mississippi River. seeks to understand all the potenal ramificaons. Health: The stress on human health is already apparent in climate change-links to Ocean Acidificaon: The swi and recent illness and increased exposure risk. unprecedented changes to ocean chemistry Outbreaks of West Nile virus correlate with stress sea life and coral reefs that are crical higher temperatures, for instance, and heat to ecosystems. The changes have already waves are the no. 1 weather-related cause of been witnessed and tallied, as in oyster death. producon, and their impacts are on track to get much worse. Extreme Weather: Extreme weather offers perhaps the most tangible fingerprint of climate change. As more people experience unprecedented heat waves, extreme precipitaon and drought, they are beer able to wrap their minds around the scale of

6 Science Media

Science has advanced dramacally in the last Domesc disasters are widely reported by several years, and the ability to fingerprint the news media, fill social media channels, (or aribute) many events, disasters, and and are a mainstay of kitchen table trends to climate change now exists.16 conversaon. Americans are parcularly Climate disrupon has greatly amplified and good listeners when the story is unfolding in fueled many disasters, such as Superstorm their own backyard. Because news focuses Sandy17,18 and western wildfires.19 In other the public on damage and disaster, it offers a disasters, tremendous climate change opportunity to has so put climate dramacally change in the increased the spotlight. odds of the underlying While media event (such as coverage in the case of linking climate the recent change to record- disasters sll breaking heat oen falls wave in Texas) short, the it can be said situaon has that climate improved disrupon is Jim Cantore, an on-camera meteorologist for The Weather significantly the primary Channel, reports on Hurricane Irene from Baery Park in over the last 20 cause. New York City. two years. Photo: The Weather Channel via Gey Images Most analyses Climate show coverage change rising, and all impacts run far show a striking ahead of projecons offered by climate upturn in aenon to current climate change models. Past predicons have turned out to impacts.30,31,32 Stories linking climate change be overly cauous, oen underesmang to sea-rise, unusual weather and other the rate of change.21,22,23 events reached an all-me high in 2012. A recent analysis found 5,800 stories on Just as slow-moving impacts, such as sea impacts published in 2012, 37 percent more level rise, are constant and observable, the than 2011 and 25 percent more than during fast-moving impacts, such as extreme the 2009 peak.33 weather and wildfires, now also show clear, constant trends extending over decades. Although media coverage can sll improve, 24,25,26,27,28,29 There will be no returning to the these trends highlight the opportunity to old normal when it comes to extreme work with the news media in highlighng weather or other fast-moving impacts. climate change right here, right now.

7 Public Opinion Strategies

One of the great challenges in mobilizing For a variety of reasons, climate change acon on climate disrupon is that despite discussion typically focuses on the future. Americans’ clear concern about global Unfortunately this approach reinforces the warming, most see the maer primarily as a percepon that climate change is not an problem for the future.34 This helps explain immediate concern. Switching the focus to the low priority Americans assign the issue highlight current climate impacts means when ranking it against other pressing talking about the here and now. naonal concerns for immediate naonal acon.35 The link between climate disrupon and current impacts is parallel to the link However, over the last three years there has between cancer and smoking. Much like the been a steady and significant rebound in Surgeon General needed a simple message Americans’ recognion of global warming, to convey the risks of smoking, speakers on parcularly among Republicans.36,37,38 global warming need to lead, connue, and end with the simple overarching statement This sea change was driven largely by that climate change is here and now. personal experience and media coverage of warmer temperatures, extreme weather, and the loss of iconic Arcc sea ice. 39,40,41,42,43

Majories of Americans are now connecng the dots between global warming and extreme weather. This gives advocates a plaorm for highlighng climate disrupon and damage across the U.S. It also underscores the value in doubling down, as polical science suggests, to focus on current climate impacts. When it comes to cigarees, public health advocates have figured it out. Keep it simple, strong, and relevant, like this warning label. Photo: Collecva/Alamy

8 One way to connect climate change to distracng, it is more effecve to frame current events is to link events and impacts climate change as amplifying disaster — as to the ongoing trends, and then link the opposed to contribung to the underlying trends to climate change. These trends are event. the middle link between individual events and global warming. Unprecedented events Disaster usually strikes when a threshold is or events for which there are no long-term crossed, and climate change is oen the records can be linked to climate change by straw that breaks the camel’s back. It is explaining how they are consistent with the important to point out the role of climate physical changes global warming drives. disrupon in driving disaster. Even when climate change may have only amplified the Throughout this guide, the terms global events underlying any parcular disaster, it warming, climate change and climate may have been primarily responsible for disrupon are used interchangeably to most of the damage. Climate disrupon turns describe the oen complex changes to global events into disasters. climate driven by human-caused warming of the planet. How far you go in connecng the dots depends on your audience. When discussing Climate disrupon can evoke the destrucve disaster and extreme events, introduce impacts that change alone fails to fully climate disrupon as appropriate. Talking convey and avoids the counter-intuive about choices can help move a discussion assumpon that warming could not also about preparaon (adaptaon) to a bring other impacts, such as intense winter conversaon about prevenon (migaon). storms. How far we go in preparing for global warming depends upon how much climate It is useful to link climate disrupon to the change we prevent. We know an ounce of damage incurred in a disaster rather than to prevenon is worth a pound of cure, and we the underlying event. In some instances, need to act now to prevent climate climate change magnifies the scope of a disrupon from becoming much worse. disaster. Because explaining causality can be

9 Communicaon Guidelines

Talk About the Here and Now speakers on global warming need to lead, Focus first on the here and now, not on what connue, and end with the simple might come later. Too oen speakers focus overarching statement that climate change solely on the potenal of future climate is here. change impacts to warn against inacon in controlling carbon polluon. This approach Link Damage and Disasters to the Larger reinforces the percepon of many Americans Trends that climate change is primarily an issue of These trends are the middle link between the future.44 Unfortunately, this frame individual events and global warming. undermines any sense of urgency. Connect the dots by starng with the current event, explain how it is consistent Paint the Big Picture with the ongoing trend, and then link that It is important to frame conversaons, trend to climate change. Consider, for including discussions about individual example, these trends and impacts: events and disasters, by making the Increasing drought and interrupons in food fundamental connecon: climate change is supply; increasing extreme precipitaon, happening right here, right now. Much like flooding and disrupon in transit and the Surgeon General needed a simple transportaon; increasing heat waves and statement to convey the risks of smoking, mortality among the ill and elderly.

Climate-related natural disasters have already increased in the U.S. Source: Munich Re, NatCatSERVICE

10 Highlight the Strongest Link scope of a disaster, such as the rising sea When linking climate disrupon to individual levels that pushed up the surge from events with mulple climate change Superstorm Sandy. At other mes, global connecons, start with the links where the warming contributes directly to the event science is strongest. For example, in the itself, such as in the case of heat waves. But disaster brought on by Superstorm Sandy, even then, explaining causality can be the strongest link to climate change is found distracng, and there are other instances in the elevated sea levels that increased the where the connecons are very complex. In reach of the storm’s sea surge, significantly general, frame climate change as amplifying amplifying the cost of the disaster. the disaster as opposed to contribung to the underlying event. This can help avoid an Focus on Climate Disrupon overly narrow conversaon focused on Talk about climate disrupon, rather than whether climate change “caused” an event. climate change or global warming. This helps avoid counter-intuive framing, such as Invoke Thresholds for Assessing Damage warming causing extreme winter storms in and Disaster the U.S., which can be confusing though Disaster usually strikes when a threshold is factual. It also helps your audience crossed, and climate change is oen the understand how a small change in the straw that breaks the camel’s back. Human average global temperature can have a major infrastructure and natural systems have impact on extreme events. The average developed to cope with historical extremes temperature during the last Ice Age was only such as 100-year events. New, more intense 9˚ F cooler than recent condions. extremes can overwhelm and collapse exisng human systems and structures.45 Connect Climate Disrupon to the Disaster Although climate change may have only Link climate disrupon to the collateral and contributed to or amplified the events direct damage incurred by the event, rather underlying any parcular disaster, it may than just to the event itself. In some have been primarily responsible for most of instances, climate change magnifies the the damages. Climate disrupon turns an extreme event into a disaster.

Talk About What You Know “When we see records being Don’t start with what you don’t broken and unprecedented events know. Don’t lead, for instance, by such as this, the onus is on those saying you can’t blame a parcular who deny any connecon to disaster on climate change. climate change to prove their Conversaons in the media are case. Global warming has extremely short and oen framed by fundamentally altered the the very first thing we say. In this background condions that give context, explaining that we cannot rise to all weather. In the strictest blame individual events on climate sense, all weather is now change is confusing at best and connected to climate change.” misleading at worst. Instead, start

with what you do know, and build – Dr. Kevin Trenberth, Naonal from there. Center for Atmospheric Research

11 Highlight Broken Records Emphasize Unprecedented Events Record seng events are a signal of climate Don’t shy away from linking climate change. They grab aenon and offer an disrupon to unprecedented events, intuive understanding of climate change. parcularly when the event is consistent with Records tend to be broken when natural the basic physical changes driven by global variability runs in the same direcon as a warming. By definion, there are no long- trend driven by global warming. term trends for unprecedented events, so that method for assessing the link to climate change is not available. Climate models tend to be poor at simulang the kinds of atmospheric circulaon changes, such as “blocking,” that foster many unprecedented weather events, making that kind of analysis less than reliable. However, unprecedented events are exactly what climate change produces. Any parcular event could represent the wild cards introduced by climate New record high temperatures have consistently disrupon. In the strictest sense, outnumbered record lows. Source: Meehl et al. and NOAA all weather events are now affected by climate change, so the burden of proof becomes Focus on Frequency and Severity showing that something other than climate A small change in average global change is fully responsible.48 temperature leads to a very large change in the frequency of the most extreme events.46 Know the Signatures of Climate Change Extreme events are rare. However, a small The signatures of climate change vary for shi in temperatures bumps these events different kinds of impacts and for different toward the middle range where events are regions. Learn the signatures of climate much more commonplace. For instance, change for your region. Get the language NOAA found that the intensity of a heat right. The relaonship between impacts and wave in Texas equal to the state’s recent climate change is complex, and opponents record-breaking heat wave is now 20 mes will jump on mistakes. Learn the science and more likely due to climate disrupon.47 The the right phrasing to link current impacts and most severe events are exactly the kind of disasters to climate change (see secons events that are the most likely to have below). become much more frequent due to climate change.

12 Don’t Debate the Science While global warming is now a contribung Spending too much me rehashing denier factor to all weather events, natural variaon talking points can reinforce the idea that has always been, and will connue to be, a the science is controversial. Instead, it is major determining factor for day-to-day beer to simply point to trusted weather. It is important to start authories who have validated the reality conversaons about extreme weather events of climate change and its current impacts, by spotlighng and explaining their such as NOAA, NASA and the U.S. Naonal connecon to global warming. Nevertheless, Academy of Sciences, as well as the as the conversaon deepens and gains insurance industry and the U.S. military. nuance, you can preempt arguments about natural variaon by explaining how climate Don’t Debate the Consensus disrupon dramacally changes the Explain the existence of deniers by frequency and intensity of the weather comparing them to those who denied the delivered by natural variaon. However, consensus on smoking for many years aer remember the goal is not to deliver a science the Surgeon General’s warning. lesson, but to answer the queson that Americans want to know: are current Push Back extreme events related somehow to global Quesoning the link between climate warming? change and extreme events is no different than quesoning the link between smoking Know Your Audience and cancer. It is important to assert that Consider your audience when deciding how the science is extremely strong. explicitly to connect the dots. When discussing disaster and extreme events, Preempt Alternate Explanaons introduce the role of carbon polluon in Somemes natural variaon, El Niño, driving climate disrupon as appropriate. blocking events and other circulaon Somemes you may not be the best changes are invoked as the cause of spokesperson for your audience. Use the unprecedented or record-breaking extreme messengers most trusted by those who you weather. You can preempt these arguments are trying to reach. by accounng for them in your communicaon. These kinds of “explanaons” amount to nothing more than a descripon of the larger event. They do not idenfy the ulmate drivers of the event, among which climate change should be counted. Invoking a circulaon change as the cause of an extraordinary and unprecedented extreme weather event is like saying the engine was responsible for accelerang the car. The real queson remains: where did the extra fuel come from? One contribung factor is climate change.49

13 Signatures of Climate Change

Extreme Weather atmosphere has increased the probability of record-breaking temperatures 15-fold.63 The The effects of climate change differ across signal of climate change is reflected in regions and in relaon to sectors of society record-breaking heat waves, as records are and its systems, so it is important to know more likely to be broken when climate change runs in the same direcon as natural and highlight the signatures of global variaon.64 warming according to individual impacts. Cold Spells Heat Waves Cold spells can be driven by disrupon of For heat waves, focus on the intensity, regional circulaon paerns such as the jet duraon and frequency of events, as climate stream. While average global temperatures change amplifies each of these rise with global warming, individual regions characteriscs. Strikingly, a small change in can experience unusually cold weather if average global temperature leads to a they are in the path of changing weather dramac change in the frequency of extreme paerns circulang cold air from places such 50,51 events such as heat waves. as the arcc.65 Natural variaon will connue to bring cold weather. Look for cold spells Since 1950, the number and duraon of heat associated with unusual weather paerns 52 waves worldwide has increased. The linked to climate change, such as increased hoest days and nights have become hoer “waviness” in the jet stream. and more frequent.53,54 And in the past several years, the global area hit by extremely hot summerme temperatures has increased 50-fold.55

The fingerprint of global warming has been firmly idenfied in these trends. 56,57,58 The signal of climate change can be seen in the trend toward hot nights, hot days, and high humidity.59,60,61

In the United States, new record high temperatures now regularly outnumber new record lows by a Temperatures were over 20 degrees F (dark red areas) rao of 2:1.62 And for the U.S., the above average during the heat wave of spring 2012. rise in heat-trapping gases in the Source: NASA

14 Rain and Snow witnessed a 20 percent increase in the amount of precipitaon falling in the For rain and snowfall, it is important to focus heaviest downpours. In the Northeast, the on the trends driven by climate change amount of precipitaon falling in the specific to each region. Global warming has heaviest 1 percent of events has increased changed the geographic paern of 67 percent over the last 50 years.70 precipitaon; some areas are geng drier while others are geng weer. At the same Storms supplied by climate change with me, climate change has increased the increasing moisture are widely observed to intensity of precipitaon across the world. produce heavier rain and snow.71 NOAA When it rains now, it really does pour. reports that the record-breaking rainfall dumped by Hurricane Irene was the primary Even areas that see less precipitaon impact of the storm in the United States, overall now experience this trend of with flooding and other damage totaling concentrated downpours. Focusing on more than $15 billion.72 intense rainfall events, then, is a powerful way to highlight the impact of climate In addion to concentrang rain and change regardless of region.66,67,68,69 snowfall into heavier events, climate change also has dramacally reworked the paern of One of the clearest changes in the weather wet and dry areas around the world. While across the U.S. is the increasing frequency total global precipitaon has remained flat or and intensity of heavy rain and snow. For increased slightly, dry areas are becoming example, in the past century we have drier and wet areas weer.

Mid-latude areas, such as the U.S. Midwest and Northeast, have experienced an increase in total precipitaon. Sub- tropical areas, such as the U.S. Southeast and Southwest, on the other hand, have experienced a sharp decrease. As a result, the risk of both drought and flooding in the U.S is increasing.73,74

Some sub-tropical The percentage of the country affected by either extreme drought or areas, such as Texas, extreme rainfall has increased. Source: NOAA have not witnessed clear changes in long-

15 term precipitaon trends, but recent Drought has become more frequent and shoralls in precipitaon are consistent with intense in some regions of the U.S. The the global changes driven by climate change. drought over the last decade in the western 75 U.S. represents the driest condions in 800 years.78 Heavier snowfalls are also consistent with climate change. A warmer atmosphere holds more water, which will connue to fall as snow as long as winter temperatures don’t rise above freezing.76 The U.S. Northeast, for example, has experienced a dramac increase in one-day precipitaon extremes during the October to March cold season.77

Drought Farmer Steve Niedbalski of Nashville, IL shows the effects of Global warming drives drought on his corn. The drought of 2012 has been devastang drought through changes in to farmers. both precipitaon and Photo: Seth Perlman, AP temperatures that vary by region, so it is important to focus on the climate change- driven trends specific to the local region. Worldwide, climate change tends to cause Watch, too, for large swings between dry areas to become drier. Moreover, areas drought and flood, a paern consistent with around the world are seeing increasingly global warming. wide swings between wet and dry extremes, another hallmark of climate change.79,80 Depending on a region’s latude, climate change can reduce or increase the total The different ways climate change can drive annual precipitaon. It can also concentrate drought can be observed across the United the year’s precipitaon into fewer but States. The U.S. Southwest has experienced heavier downpours. This can lead to more climate change-amplified drought through 81 run-off and, in turn, contribute to drought. higher temperatures and loss of snow pack. Texas has experienced climate change-fueled Global warming can also raise local drought through recent record heat waves, 82,83,84 temperatures and drive more frequent and which dry out soils. And dramac intense heat waves, all of which can dry out swings between drought and flooding in the land and prompt the early melt of snow pack, Southeast U.S. have been linked to changes another contributor to drought. in the North Atlanc Subtropical High, another result of global warming.85

16 Flooding even months. The frequency of great floods (100-year floods in large basins) around the Flooding can be parcularly tricky to discuss. world has increased over the course of the In addion to changes in extreme weather 20th century.95 Recent periods of sustained (which vary regionally), flooding is affected rain in the U.S. Midwest and Northeast are by factors such as land development, consistent with the shi of the mid-latude deforestaon, levee placement and local rain belt, which has been pushed northward topography.86 by changes in atmospheric circulaon driven by global warming.96 Focus on floods consistent with regional climate change trends, such as an increase in Flooding in the northern half of the eastern heavy rain and snow, early snowmelt, and Great Plains and much of the Midwest has increased seasonal precipitaon. All of these been increasing, especially over the last trends may be linked back to climate change several decades. In the areas of greater depending on the region.87,88 Watch, too, for flooding, increases in both total precipitaon large swings between drought and flood, a and extreme precipitaon contribute.97 Very paern consistent with global warming.89 heavy, sustained rains drove record-breaking Mississippi River flooding in 2011. Such long- Heavy precipitaon is contribung to term heavy precipitaon events are increased flooding around the world.90,91 becoming more common. In the U.S., 90-day Very heavy precipitaon has increased over periods of heavy rainfall were 20 percent the past century in many parts of the U.S. more common from 1981 to 2005 than in The largest increases have occurred in the any 25-year period on record.98 Northeast, Midwest, and Great Plains, where heavy downpours have exceeded the capacity of infrastructure such as storm drains and have led to flooding events.92 The extreme precipitaon during both the Nashville flood of 201093 and Hurricane Irene94 illustrate this trend.

In contrast to flooding driven by short-term extreme precipitaon, flooding in large river basins, such as the Superstorm Sandy caused unprecedented flooding in the subways of Mississippi, is caused by New York City, with massive costs. Photo: Timothy A. Cleary, Gey Images seasonal precipitaon persisng for weeks or

17 Storms releases heat energy that adds buoyancy to the air and fuels the storm. This increases the For storms generally, focus on their intensity gathering of moisture into storm clouds and and heavy rainfall. [Note: see specific further intensifies precipitaon.102 guidelines for hurricanes and tornadoes below.] Climate change loads storms with For winter storms, use the term climate more energy, thus increasing intensity. All disrupon to help explain the link to winter storms, including thunderstorms, snow storms instead of counter-intuive terms storms, and tropical cyclones, are now such as global warming. Climate disrupon in developing in a warmer, moister the Arcc occasionally lets loose severe environment.99 General storminess around winter storms that sweep down and over the the world, as measured by winds speeds and United States.103 ocean wave heights, has increased in recent years, parcularly during winter months.100 Hurricanes

Consistent with a warming climate, a 4 For hurricanes, focus on the role global percent increase in atmospheric moisture warming plays in increasing heavy rains and has been observed.101 Storms reach out to on the contribuon of global warming to gather water vapor over regions that are 10 higher storm surge through rising sea levels. to 25 mes as large as the precipitaon area, The science is strongest on these links, and thus mulplying the effect of increased for many storms, the damages wrought by atmospheric moisture. As water vapor heavy rain and storm surge are oen much condenses to form clouds and rain, it worse than the damage from heavy winds.

Global warming is already loading hurricanes with addional moisture that makes rainfall more intense. Global warming meant Hurricanes Katrina and Ivan, for example, carried significantly more rainfall. In the case of Katrina, that increase may have contributed to the breach of the levees in New Orleans.104,105

At the same me, hurricane storm surge now rides higher on seas that have risen over the last century, much of which is aributable to melng ice sheets and a warmer, expanding ocean. Rising sea levels give storm surge a higher plaorm for jumping Ocean heat content has greatly increased since 1950, onto land.106 Over the last and more heat in the ocean means more energy for century sea level has risen nearly storms and hurricanes. Source: Center for Australian a foot in the New York harbor, for Weather and Climate Research instance, one of the locaons

18 damaged worst by the storm surge thrown Tornadoes up by Superstorm Sandy.107 Due to poor quality records, the long-term There has been a substanal increase in trends in tornadoes over the last century are virtually every measure of hurricane acvity unclear.123,124 Be careful with the science in the Atlanc since the 1970s. These connecng tornadoes to climate disrupon. increases are linked, in part, to higher sea While there is considerable evidence, the full surface temperatures in the region that story is not yet known and important pieces Atlanc hurricanes form in and move are sll missing. To connect the dots, it is through. Numerous factors influence these best to simply note that an increase in local sea surface temperatures, including tornadoes is consistent with the warmer, human-induced emissions of heat-trapping weer world created by climate change, and gases and parculate polluon and natural that parcularly large and unprecedented variability.108 tornado events MAY represent the results of climate disrupon. Focus in parcular on Substanal evidence indicates that global intense February tornadoes and tornadoes warming also may be responsible for the appearing well north of usual. recent increasing intensity of Atlanc hurricanes,109, 110,111,112,113,114 for the Note that 2011 was the second-most acve increasing size of hurricanes115 and a year in the tornado record, and 2004 ranked lengthening hurricane season.116 Out of the as the all-me most acve year.125 11 most intense North Atlanc hurricanes Meteorologists report that in recent years ever recorded, five have occurred in the last tornadoes have appeared well north of usual eight years (Wilma, Rita, Katrina, Dean and latudes and have been unusually intense Ivan).117 There is some debate, however, early in the calendar year.126 February 2008 over whether one can confidently aribute was the most acve February in the modern these recent trends to global warming due to record; February 2010 the fourth most-acve the incomplete historical record over the last and February 2012 the fih-most acve. The 150 years118 and the complex interacon of five largest early- season two-day outbreaks the factors that govern hurricane formaon. have all occurred since 1997, and three of 119 the top five outbreaks occurred in the last four years.127 Looking forward, there is a consensus among experts that global warming will create Is global warming influencing tornadoes? stronger hurricanes.120,121 Although the According to the Naonal Oceanic and global tropical cyclone count may decline Atmospheric Administraon (NOAA), the slightly, the science projects a dramac best answer is: “We don't know.”128 increase in the number of very strong However, tornado spikes, parcularly early hurricanes in the Atlanc.122 Unfortunately, season tornadoes and tornadoes further these two trends may not balance out, as the north than usual, are consistent with the damage caused by stronger hurricanes is warmer, weer world brought on by climate exponenally greater than the damage change. The computer models that illustrate wrought by lesser storms. As such, one can our best understanding of climate in a say that as global warming becomes locked warming planet indicate that the condions in, the damage brought on by parcularly that foster the thunderstorms that spawn strong hurricanes will grow. tornadoes may increase in some regions and

19 stronger tornadoes will become more esmated value of $136 billion — are located frequent.129,130 in areas deemed at high risk of wildfire.137

Wildfires In the midst of severe drought in the summer of 2011, Arizona and New Mexico suffered Climate disrupon has amplified the threat the largest recorded wildfires in their of wildfires. This is parcularly true for the recorded history, vividly illustrang how western United States. To make climate different elements of climate change can connecons, focus on the length of the fire interact to escalate events into a disaster. season and the size of fires. Watch for new Following the fire, heavy rainstorms led to fires burning in regions where fires were not major flooding and erosion, including at least witnessed before. 10 debris flows that caused costly damage to drinking supplies. Sediment and ash eroded In the western United States, both the by the floods were washed downstream into frequency of large wildfires and the length of the Rio Grande, which supplies 50 percent of the fire season have increased substanally drinking water for Albuquerque, the largest in recent decades. Earlier spring snowmelt city in New Mexico. The city stopped water and higher spring and summer temperatures withdrawals for a week and reduced them drive this change.131,132 Climate change has for six months due to the increased cost of increased the threat of “mega-fires” – large treatment.138 fires unprecedented in their impacts.133 Warming has also led to wildfires present in regions where they have been absent in recent history.134

Climate change is also promong bark beetle outbreaks: these pests breed more frequently and successfully in warmer winter condions. And the dead trees le behind by bark beetles make crown fires more likely.135

Average fire size in 2012 was largest on record. More than nine million acres burned in 2012, the 3rd highest total on record behind 2006 and 2007, and damages topped $1 billion Higher average spring and summer temperatures correspond dollars.136 More than with more forest fires on U.S. Forest Service land. 740,000 homes in 13 Source: Climate Central western states— with an

20 Season Creep

As climate change connues to advance, spring is arriving much sooner, while winters are becoming shorter and milder. This phenomenon has been documented around the world and informally dubbed “season creep.”139,140

Global warming drives season creep.141 Natural variability can, at best, explain only one-third of the rate of “creep” in the arrival of spring.142

Season creep is an example of how small changes can have a big impact; climate change disrupts the crically important ming of events, such as snow melt and spring bloom, upon which ecosystems and Rick Hardy of the Brookdale Fruit Farm shows agricultural industries depend. Focus on peach blossoms that opened early due to warm these disrupons to highlight climate change weather, but then were damaged by frost. They here and now. will bear no peaches, causing him financial loss. Photo: Bob Hammerstrom In the United States, spring now arrives an average of 10 days to two weeks earlier than cold temperatures for strong sap flow and it did 20 years ago.143 Growing seasons have 144 good flavor, and the brevity of recent winters lengthened by 10-20 days. Many migratory has cost producers.150 bird species are arriving earlier. For example, northeastern birds that winter in the Finally, season creep is impacng southern United States now return to the 145 biodiversity, with cascading effects on Northeast an average of 13 days earlier. agriculture, tourism, hunng, and fishing. All Spring snowmelts have shied so that peak 146 species do not respond to the change of melt flow now arrives 1-4 weeks earlier. seasonal cues in the same way. This can lead Flowers are blooming earlier, including a to mismatches between the availability of week earlier on average for Washington 147 flowers and their pollinators or predators D.C’s famous cherry blossoms. Hardwood and their prey.151,152 For example, the pied forests are holding their green leaves 10 days 148 flycatcher now migrates at the wrong me longer. relave to its prey and has experienced a 90 percent populaon decline.153 In some cases, Season creep is impacng a wide range of these disrupons can enable takeover by industries. For example, warmer winters can invasive species, as witnessed at Thoreau’s lead to early bud-burst or bloom of some Walden Pond.154 perennial plants, resulng in frost damage when cold condions occur in late spring, as was the case with Michigan cherries in 2012.149 Maple syrup producon requires

21 Arcc Sea Ice recent record-breaking melt seasons. The summer melt of 2012 reached an all-me The massive loss of iconic sea ice in the Arcc record low, with sea ice extent falling to 50 is one of the most powerful indicators of percent of the historic average. The record climate change and resonates strongly with low of 2012 was 18 percent below the prior the American public. When public opinion record low set in 2007. And the total amount surveys ask respondents to explain why they lost was equivalent in size to 43 percent of recognize global warming, sea-ice loss is one the conguous United States.157,158 of the primary factors cited.155,156 Currently, Arcc sea ice serves as the planet’s To discuss the impact of global warming in air condioner, moderang solar heang by the Arcc, highlight the 50 percent summer increasing the reflecvity of Earth’s surface sea ice loss and the Arcc’s diminished and decreasing the amount of heat that capacity to work as the planet’s air would otherwise be absorbed by ice-free condioner in moderang global Arcc seas. The loss of the air-condioner temperatures. Addionally, link to effect, as sea ice disappears, creates a disrupons in Arcc weather paerns that feedback loop that accelerates global have recently surfaced and are driving warming.159 extreme weather (in parcular, harsh winter storms) down to the lower 48 states. Arcc sea ice has been retreang over the past 30 years, and the rate of retreat is Due to a combinaon of greenhouse gasses accelerang at a pace that exceeds most and its unique climate feedbacks, the Arcc models’ forecasts.160 Research shows that has been warming at double the rate of the before the 20th century’s influx of rest of the globe. This is causing an greenhouse gasses and subsequent period of unprecedented and rapid retreat of thick Arcc sea ice retreat, the Arcc was in a Arcc sea ice. The signature of climate 2,000-year cooling trend.161 change has been firmly documented in the

Arcc sea ice has shrunk dramacally. Source: Melillo et al. 2013

22 Changes in the Arcc, especially sea ice loss, states. Some well-known glaciers, such as are affecng weather paerns in the lower those in Glacier Naonal Park, are on the United States. The loss of Arcc summer sea verge of disappearing altogether. Melng in ice and the rapid warming of the area alter Greenland is parcularly dramac and has the jet stream — and thus weather paerns the potenal to become as powerful a — over North America, Europe and Russia. climate change signal as Arcc sea ice loss. These changes increase the likelihood of extreme weather and drive winter storms The glaciers and ice sheets of Greenland are south.162,163 among the largest bodies of fresh water on the planet. The surface of the Greenland ice If heat-trapping polluon connues, summer sheet has been experiencing summer melng sea ice will be lost enrely. The climate over increasingly large areas during the past models that most accurately simulate past several decades. In the decade of the 2000s, sea ice trends suggest this will probably the daily melt area was double the happen in 22 years, possibly as soon as eight corresponding amount of the 1970s, years.164 culminang in summer melt that was far greater in 2012 (97 percent of the Greenland Ice Sheets and Glaciers ice sheet area) than in any year since satellite records began in 1979. More importantly, the Greenland rate of mass loss has accelerated in recent decades. This increases Greenland’s The melng of ice sheets and glaciers around contribuon to sea level rise.165 the world is accelerang and contribung to rising sea levels. Glaciers are retreang and/ The key issue in predicng future rates of or thinning in Alaska and in the lower 48 global sea level rise is to understand and predict how ice sheets in Greenland and Antarcca will react to a warming climate. Current projecons of global sea level rise do not account for the complicated behavior of these giant ice slabs as they interact with the atmosphere, the ocean and the land. Lack of knowledge about the ice sheets and their behavior is the primary reason that projecons of global sea level rise include such a wide range of plausible future condions that include more than 6 feet of sea level rise in the coming decades.

The massive weight of Greenland’s ice sheet physically pushes the island down into the ocean. As the ice sheet melts and the weight decreases, the island rises in response. In recent years, so much ice has melted so Greenland melt extent has been steadily quickly that the rate of Greenland’s rising has increasing over me. been accelerang since 1990s.166 Source: NASA Earth Observatory

23 Antarcca

In the face of climate change, Antarcca presents a more complex picture than its counterpart in the Arcc. Connent-wide, Antarcca has shown a posive warming trend over the last 50 years.167 However, not every region has responded in the same way. The Antarcc Peninsula has shown the strongest warming, followed by West Antarcca, while East Antarcca and the Over the past two decades, warmer temperatures have connental interior have at caused the permanent ice sheets of greenland and antarcca mes shown cooling trends.168 to melt at an accelerang rate and contribute to rising sea To explain these trends, levels. Source: The Ice Sheet Mass Balance Inter-comparison researchers note that ocean Exercise (IMBIE) currents deliver heat to the

Antarcc Peninsula and coastal regions. In the interior and eastern regions, on the other hand, reduced ozone coverage alters air currents, increases winds, and thereby diverts warm air.169,170,171

When it comes to ice, the story is similarly complicated. In spite of warming temperatures, sea ice extent in some areas of Antarcca has increased.172 Research suggests this is due to reduced mixing between warm and cool layers in the ocean that ordinarily speeds the melng of ice.173 The previously menoned wind paerns induced by ozone depleon may also The coastlines and west of Antarcca are warming, while the play a role.174 central and eastern parts are cooling. Source: NASA

24 In other, more important ways, though, accelerated, with the rate of rise doubling Antarcca is losing ice. Independent of any since 1992.181 These changes stand in stark changes to the extent, or surface area, of sea contrast to the prior 2,000 years, when there ice, new research shows that melng from was lile change.182 This rise is primarily due below is causing most of the connent’s ice to global warming.183 shelves to grow thinner, some at a rate of up to seven meters per year.175 Land ice sheets Sea level rise is already impacng coastal are melng too, at an accelerang rate of communies in the United States.184 Focus over 246 billion tons per year.176,177,178 Unlike on the impact of sea level rise in storm surge, sea ice, land ice melt contributes to sea level dal flooding and saltwater intrusion into rise. Melng of the Antarcc and Greenland fresh water aquifers. Also watch for local ice sheets alone was responsible for about a flooding compounded by intense rainfall, half inch of sea level rise since 1992.179 another impact of climate disrupon.

In summary, Antarcca is both warming in While sea level rise may be modest relave temperature and contribung significantly to to the total height of storm surge or high sea level rise. While some localized areas des, it can be the straw that breaks the may be cooling and/or gaining ice, these camel’s back. Disaster usually strikes when a examples are not enough to reverse the threshold is crossed. Human infrastructure trend. and natural systems have developed to cope with a range of historical extremes, such as Sea Level Rise 100-year events. New, more intense extremes can overwhelm and collapse Sea levels have increased by about 10 inches exisng human systems and structures.185 since they began rising in the middle of the When sea level rides on top of storm surge 19th century.180 Recently, the rise has

The impact of sea level rise is parcularly visible in coastal flooding events such as this Annapolis scene from January 2010 in which sea level rise furthered the reach of an unusual high de compound by a strong onshore wind. Photo: Chesbayprogram on Flickr

25 and high des, it can be responsible for a Ocean Acidificaon disproporonate amount of damage. Sea level rise, combined with coastal storms, Ocean acidificaon, driven directly by rising has increased the risk of erosion, storm-surge carbon dioxide levels in the atmosphere, is damage, and flooding for coastal progressing steadily and measurably and is communies, especially along the Gulf of already taking a toll on sea life. Ocean Mexico, the Atlanc seaboard, and Alaska. acidificaon is the evil twin to global Rising sea levels give storm surge a higher warming. Both stem from carbon polluon, plaorm for jumping onto land.186 Over the and the producon of CO2 emissions from last century, sea level has risen nearly a foot power plants, factories, cars and buildings in the New York harbor, one of the locaons has already pped the balance in the oceans worst hit by the storm surge driven by around the world. Superstorm Sandy.187 Coastal infrastructure including roads, rail lines, energy Focus on the link between acidificaon and infrastructure, and port facilies including carbon polluon and the parallel link naval bases, are at risk from storm surge that between carbon polluon and global is exacerbated by rising sea levels.188 warming. Highlight the current impacts of acidificaon and the risks it poses to food Higher sea levels also destroy the marshes resources, related industries and the broad and wetlands that provide coastal areas an web of relaonships between ecosystems. essenal buffer from storms and flooding. Acidificaon currently threatens sea life, Higher sea levels cause more frequent primarily by making it harder for animals with flooding from higher dal surges as well as hard shells and skeletons to access material saltwater intrusion into aquifers and to build them. Weaker and thinner shells estuaries. In regions where precipitaon increases, coastal areas will see heavier runoff from inland areas, with the already observed trend toward more intense rainfall events connuing to increase the risk of extreme runoff and flooding.189

Climate change drives sea level rise in two major ways. Warming expands the volume of water in the oceans, which pushes up sea levels. Warming also melts glaciers and ice sheets on land, with the run-off adding to sea levels. Melng sea ice is not a significant factor, as melted water mostly fills the empty volume le behind by melted ice. Regional sea levels vary based on regional and local changes in land movement and long-term changes in coastal circulaon paerns.190 Ocean acidificaon impairs the development of shellfish like this Pacific oyster. Many Looking forward, the consensus science hatcheries in the Pacific Northwest have suggests an upper limit of 6.6 feet of global already experienced declines in producon. rise by 2100 should be used Photo: NOAA for risk analysis.191

26 make sea life more vulnerable to predators, Human Health disease and death. Sciensts believe acidificaon may worsen corrosion of marine Climate disrupon is already affecng health animal shells and skeletons in the future. risks and disease vectors.200 The interacon between climate change and health is The increase in ocean acidity is indisputable, extremely complex. Focus on the current and the rate and magnitude of the change is health impacts that are consistent with the unprecedented, with a 30 percent jump since trends in the way climate change is affecng the beginning of the industrial revoluon, as the underlying risks and vectors. reported by the Naonal Academy of Sciences. The rate of change is one of the Heat-Related Illness main reasons sciensts are concerned that marine life cannot adapt quickly enough to Exposure to extreme heat is already the acidificaon.192,193 primary cause of weather-related mortality in the U.S.201 As climate change drives more The impact of acidificaon is already frequent and longer-lasng heat waves, the happening and illustrates the risks to ocean associated illness and death mulply, life and resources that both ecological and especially in metropolitan areas and economic systems rely upon. Damage from communies at higher latudes, which are acidificaon to oyster larvae in the Pacific not used to such extreme temperatures.202 Northwest has been documented,194,195 as There is a marked difference in the rate of well as poor shell development in sea snails deaths resulng from hot and cold that many whales depend upon as feedstock. temperatures. Researchers have found that 196,197 Both observaons confirm scienfic on average, cold snaps in U.S. cies increase expectaons of threats from acidificaon.198 death rates by 1.6 percent, whereas heat In addion, sciensts have discovered waves trigger a 5.7 percent increase in death damage to coral reefs consistent with rates.203 acidificaon.199 Asthma, Allergies and Lung Disease

Global warming is amplifying some of the factors that drive asthma and lung disease.204

While the Clean Air Act is helping to lower emissions of tradional pollutants that drive the formaon of ozone and smog, rising temperatures due to carbon polluon are working in the opposite direcon and promong their formaon.205 Hoer temperatures accelerate the processes that create surface ozone, a key lung irritant that In an experiment simulang water condions exacerbates lung diseases and can cause in 2100, a snail shell slowly dissolves over 45 breathing difficules even in healthy days. Current levels of acidity are enough to individuals.206 impair shell development. Source: NSF/NOAA

27 Climate disrupon has also prompted earlier Waterborne Diseases onset for the spring pollen season in the United States, and pollen allergies have Heavy rains can lead to flooding that can shied earlier in parallel.207 increase the incidence of waterborne diseases due to pathogens. Contaminated West Nile, Rocky Mountain Spoed Fever, drinking water aer a heavy rain has already and Insect Vector Diseases been linked to illness from organisms such as Cryptosporidium and Giardia.211 Downpours Climate change affects the life cycle and can trigger sewage overflows that distribuon of the mosquitoes, cks, and contaminate drinking water and endanger rodents that carry West Nile virus, equine beachgoers. During heavy rains, these encephalis, Lyme disease, Rocky Mountain systems oen cannot handle the volume, Spoed Fever and hantavirus.208 and raw sewage spills into lakes or waterways, including into drinking-water West Nile virus outbreaks have exploded supplies and places where people swim.212 across the U.S. over the last 14 years, with more than 5,000 cases recorded in 2012.209 Heavy rain and flooding can contaminate The risk of West Nile outbreak rises with certain food crops with feces from nearby more frequent heat waves, and the livestock or wild animals. This increases the epicenters of recent outbreaks have been likelihood of food-borne disease associated locaons marked by drought or above- with fresh produce.213 average temperatures.210 Cases of food poisoning due to Salmonella and other bacteria peak within one to six weeks of the highest reported ambient temperatures.214

Shellfish Poisoning

Vibrio sp. (shellfish poisoning) accounts for 20 percent of the illnesses and 95 percent of deaths associated with eang infected shellfish. There is a close associaon between temperature, Vibrio sp. abundance and clinical illness. Concurrent with rising Warmer temperatures contribute to the temperatures, the U.S. infecon rate expansion of mosquitoes and the West Nile increased 41 percent from 1996 to 2006.215 virus. Photo: Center for Disease Control and Prevenon.

28 Society and Systems last two years.220 Four out of five Americans live in counes where natural disasters have The combinaon of interlocking systems, been declared since 2006.221 The insurance such as transportaon, food, fuel and giant Munich RE reports that the number of energy, raise the risk of “cascading system weather catastrophes across the world has failures” that pose urgent risks to economies, tripled since 1980, with the greatest communies and local health systems, with increases in North America. Climate change commensurate costs.216 is helping drive this trend.222,223

The impact of climate disrupon on U.S. infrastructure is becoming increasingly apparent from both the growing number of climate-related disasters217 to the spectacular damage incurred in individual climate-related disasters.218

Focus on disasters and infrastructure damage in events consistent with the trends driven by climate This nuclear power plant, the Millstone Power Staon in CT, had change. Highlight the role to shut down a reactor due to the warmth of the Long Island that climate change may Sound. This is one of many ways climate change disrupts have played in amplifying necessary systems. Image: Associated Press the disaster and pushing the infrastructure past the point of collapse. Disaster usually strikes when a threshold is crossed. Storm surges from Superstorm Sandy swamped New York City’s subway system Sea level rise, extreme weather, heat waves and disrupted the gasoline delivery system and droughts – all stress infrastructure, from for a three-state area.224 Hurricane Irene drinking and wastewater systems to the washed out scores of roads and bridges transportaon that drives our economy and across New England.225 A nuclear reactor in the energy system that powers the naonal Conneccut shut down in August 2012 grid.219 because the water in the Long Island Sound was, for the first me, too hot to effecvely The Naonal Oceanic and Atmospheric cool the equipment.226 A record-breaking Administraon reports an increase in billion- heat wave in July 2012 melted the asphalt at dollar weather disasters across the U.S. in Reagan Naonal Airport in Washington DC, recent years, with an astonishing 25 such trapping a jet liner on the tarmac.227 Aquifers billion-dollar disasters with damages totaling that supply drinking water along the heavily more than $120 billion occurring in just the

29 populated coast of south Florida are prices that are expected to connue through threatened by saltwater intrusion caused by 2013.232 sea level rise.228 Rising food prices are dependent on many Transportaon and infrastructure are built factors, including populaon, income, and and designed to cope with historical availability of supply.233 This last factor is extremes. New, more intense extremes can parcularly affected by climate change.234 overwhelm and collapse exisng From 1980 to 2008, growing seasons infrastructure.229 The flooding of New York changed in most parts of the world. These City subways during Sandy’s storm surge and changes had a significant effect on global the topping of the levee in New Orleans corn and wheat producon, leading to a during Katrina are just two examples where roughly 20 percent increase in global prices thresholds marked the transion to disaster. for these commodies. During this me Although climate change may only contribute period, climate change resulted in a 5 to the event underlying any parcular percent increase in prices.235 disaster, it can be primarily responsible for most of the damages. Climate disrupon Rising sea levels driven by global warming turns events into disasters. can affect food producon. Higher seas make flooding in rice fields in vulnerable areas Food Price and Supply more likely, reducing yields and leading to higher prices.236 Climate change is also Climate disrupon is already affecng prices changing the distribuon of marine species, for food and crops through changes in affecng producon from fisheries as well.237 growing seasons, increasing extreme weather, rising sea levels, and warming The connecons of U.S. agriculture and food oceans. Focus on rising prices consistent with security to global condions are clearly shoralls in producon that align with illustrated by the recent food price spikes in climate change trends. 2008 and 2011 that highlighted the complex connecons of climate, land use, demand, Climate disrupons to agricultural and markets. The doubling of the FAO food producon have increased in the recent past price index over just three months was and are projected to increase further over caused partly by weather condions in food- the next 25 years. The rising incidence of exporng countries such as Australia, Russia, weather extremes will have increasingly and the U.S., but was also driven by negave impacts on crop and livestock increased demand for meat and dairy in Asia, producvity because crical thresholds are increased energy costs and demand for already being exceeded.230 biofuels, and commodity speculaon in financial markets.238 The effect of higher temperatures has already begun to occur; corn yields were affected by high nighme temperatures in 2010 and 2012 across the Corn Belt.231 The 2012 drought, the United States’ most extensive drought in decades, destroyed large areas of cropland and led to increased

30 “How Do We Know?”

The connecons between climate disrupon and impacts in the United States are numerous, strong and well documented. Authoritave science instuons including NASA,239 NOAA,240 the U.S. Naonal Climate Assessment,241,242 and the U.S. Naonal Academy of Sciences243 have each assessed and validated these changes. And the rising cost of these impacts has been clearly ed to climate change.244,245,246

Several types of scienfic query/invesgaon show us how climate change is already affecng the United States.

The first line of proof is by direct scienfic measurement. Many impacts such as extreme weather, drought, ocean acidificaon and sea level rise have been rigorously measured. The changes are long-term, dramac and unequivocal. And the measurements have been widely assessed and validated.

Basic physical principals offer the second proof. For example, we know that a warmer atmosphere holds more energy and more heat. Thus, global warming accounts for why the hoest days are now hoer in the United States. Or, in another example, we know that a warmer atmosphere holds more moisture, which is why the heaviest rainstorms in the United States now dump more water than before.

The computer models that simulate the climate offer the third line of proof. These models can only replicate current climate impacts when carbon polluon is put into the models. Although the models are built to simulate natural variability, the models can’t produce the trends we observe in the real world based on natural variability alone. The strength and length of the trends, as well as the incidence of unprecedented events, go far beyond what natural variaon could possibly explain. In some cases, trends have actually goen worse despite the counter-acng direcon of natural variaon. For instance, prior to global warming, the long-term trend in global temperatures was toward cooling. If all other factors that affect global temperatures had remained unchanged, the recent decline in the sun cycle should have driven a slight dip in global temperatures. Instead, global temperatures rose.

The rising cost of the disasters related to these impacts is also clearly ed to climate change. The rise in costs goes far beyond what can be explained by populaon growth or increased exposure of buildings and communies due to increased wealth.247,248,249 Climate change turns events into disasters. While climate-related catastrophes around the world have surged, rates of geophysical disasters, such as earthquakes, have remained largely level.

31 Example Language

This early outbreak of allergy season is Climate disrupon in the Arcc is bringing consistent with global warming that has harsh winter storms like this one down already moved up the spring start date by into the U.S. 20 days. Climate change is amplifying this drought This disaster is what climate disrupon through higher temperatures that dry out looks like. soils.

Extreme weather, which is fueled by Water supplies are low due to early snow climate change, drove this spike in food melt driven by global warming. prices. The feast or famine swings between flood Asthma sufferers are among those hit and drought on the Mississippi River are hardest as air quality worsens with consistent with climate disrupon. warming and climate change. Unprecedented events like this super Climate change amplified this disaster and swarm of tornadoes may represent the was the straw that broke the camel’s wildcards that global warming has back. introduced into the climate.

Global warming is feeding this heat wave. Global warming is the climate on steroids. Like a player hing more home runs on Global disrupon is driving extreme steroids, heat-trapping gases from storms and flooding like this. smokestacks and tailpipes are fueling more extreme weather like this. The storm surge in this hurricane rode on sea levels that have risen due to global This heat wave is just one event in the warming. Global warming raises sea larger trend toward longer, hoer and levels, so storm surge in hurricanes like more frequent heat waves, driven by this now reaches further inland. global warming.

Ocean acidificaon is creang hosle Global warming has stacked the deck condions for sea life, such as the with extra aces, making events like this problems for oyster farms in the both more frequent and more severe. Northwest. Climate change has loaded the dice, Global warming is driving up sea levels, making events like this more increasing the reach of high-de flooding frequent. in our region.

32 Acknowledgements

Author: Hunter Cung

Contribung writers and researchers: Lauren Baum, Stephanie Hanson Damassa, Evan Griswold, Phillip Newell, Lynsy Smithson-Stanley, Robert Tanner, Diana Van Vleet, Nora Vogel.

For more informaon contact:

Hunter Cung Director of Strategic Communicaons Climate Nexus +1 415-420-7498 hcu[email protected]

33 Endnotes

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34 116. Kossin 2008 154. Scienfic American April 197. Seibel and Dierssen 117. Naonal Hurricane 21, 2010 2003 center 2012 155. Borick and Rabe 2011 198. Cooley and Doney 2009 118. Knutsen et al. 2010 156. Borick and Rabe 2012 199. Hoegh-Guldberg et al. 119. Melillo et al. 2013 157. Perovich et al 2012 2008 120. IPCC SREX SPM 158. Melillo 2013 200. Karl et al. 2009 121. Melillo et al. 2013 159. Melillo 2013 201. Luber and McGeenhin, 122. Knutsen et al. 2011 160. Stroeve 2007 2008 123. Naonal Science and 161. Kaufman, et al. 2009 202. Luber and McGeehin, Technology Council 162. Francis & Vavrus 2012 2008 2008 163. Melillo 2013 203. Karl et al. 2009 124. Seneviratne et al. 2012 164. Melillo et al. 2013 204. Karl et al. 2009 125. NOAA Storm Predicon 165. Melillo 2013 205. Karl et al. 2009 Center 166. Jiang et al. 2010 206. Perera and Stanford 126. Ostro 2011 167. Steig 2019 2011 127. NCDC U.S. February 168. Steig 2009 207. Karl et al. 2009 Tornadoes 169. NASA Earth Observatory 208. Karl et al. 2009 128. NOAA Tornado FAQ 2006 209. CDC 2012 129. Trap et al. 2007 170. Schmidt 2004 210. Karl et al. 2009 130. Lee 2011 171. Thompson and Solomon 211. Frumkin 2008 131. Melillo et al. 2013 2002 212. Karl et al. 2009 132. Karl et al. 2009 172. Zhang 2007 213. Karl et al. 2009 133. Melillo et al. 2013 173. Zhang 2007 214. Karl et al. 2009 134. Melillo et al. 2013 174. Turner et al. 2009 215. Karl et al. 2009 135. Melillo et al. 2013 175. Pritchard 2012 216. Wilbanks and 136. NCDC State of Climate 176. Velicogn 2009 Fernandez, 2012 Wildfires 2013 177. Allison et al. 2009 217. Hoeppe 2012 137. Bos et al. 2012 178. Shepherd et al. 2012 218. Wilbanks and Fernandez 138. Karl et al. 2009 179. Shepherd et al. 2012 2012 139. Maxwell 2007 180. Hunter and Allison 2012 219. Karl et al. 2009 140. Gabay 2006 181. Melillo et al. 2013 220. NCDC Billion Dollar 141. Melillo et al 2013 182. Titus et al. 2009 Disasters 2012 142. Ault et al. 2011 183. Melillo et al. 2013 221. Dutzik and Wilcox 2012 143. Melillo et al. 2013 184. Melillo et al. 2013 222. Hoeppe 2012 144. Linderholm 2006 185. Peterson et al. 2008 223. Kuczinski and Irvin 2012 145. Melillo et al. 2013 186. Hoffman et al 2010 224. New York Times, Nov. 6, 146. Stewart et al. 2005 187. Grannis et al. 2010 2012 147. Smithsonian 2000 188. Mellilo et al. 2013 225. Marks et al. 2012 148. Richarson et al. 2006 189. Mellilo et al. 2013 226. Associated Press, August 149. Melillo 2013 190. UC-Boulder 2012 13, 2012 150. Burlington Free Press, 191. Melillo et al. 2013 227. Washington Post, July 7, March 22, 2012 192. Morel et al. 2010 2012 151. Karl et al. 2009 193. NOAA PMEL 228. Berry 2012 152. Melillo et al. 2013 194. Barton et al. 2012 229. Peterson et al. 2008 153. Both et al. 2006 195. Grossman 2011 230. Melillo et al. 2013 196. Bednaršek et al. 2012 231. Melillo et al. 2013

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