Today we’re updating our online map providing an overview of extreme weather events in the United States since 1990. The map highlights memorable examples of extreme heat, heavy precipitation, drought, and wildfire, four types of events with clear trends connected to climate change.
I recently responded to a question on the National Journal blog, "Does climate change cause extreme weather like the heat waves much of the country has been enduring for the past few weeks?"
With the Senate set to vote today on fixes to the ailing National Flood Insurance Program (NFIP), a new C2ES brief explains why the program is chronically in debt to the U.S. Treasury, and how to make it solvent. We urge, among other things, that Congress allow federal underwriters to begin taking into account rising flood risk due to climate change.
The 44-year-old federally-backed NFIP covers 5.6 million American households and more than $1 trillion in assets in flood-prone areas along rivers and coasts. Flooding is not an easy risk to insure, so historically private insurers chose not to. But in assuming that role, the NFIP has at times served to encourage rather than contain risk, and has racked up $18 billion in debt in the process.
With headlines like “Warmest spring heats up economy,” readers weary of bad economic news might be forgiven for thinking that a little global warming is not such a bad thing. But the warming we’ve experienced globally over the past 30 years is more than “a little.” And in the U.S., it’s likely contributing to drought and wildfires in the West and more extreme weather nationwide.
This past May came in as the second warmest on record globally, trailing only May of 2010. For land area only, it was the warmest on record, at 2.18 degrees F above average. It was also the 36th consecutive May, going back to 1976, with global temperatures above the 20th-century average.
Back in November the Intergovernmental Panel on Climate Change (IPCC) released the executive summary for a “special report” called Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX for shorthand). Today, the IPCC released the full technical report that underlies the executive summary. In addition to documenting the scientific evidence that extreme weather events are on the rise, the report provides a risk-based analysis of how society can best respond to the climate threat. In the words of Chris Field, co-chair of one of the two working groups that produced the report:
“The main message from the report is that we know enough to make good decisions about managing the risks of climate-related disasters. Sometimes we take advantage of this knowledge, but many times we do not. The challenge for the future has one dimension focused on improving the knowledge base and one on empowering good decisions, even for those situations where there is lots of uncertainty.”
If you live in the central or eastern United States and have been outside lately, you can attest to the downright summery weather we’ve been experiencing. In fact, this March weather is not just unusual; it is unprecedented. In Detroit, there has not been a comparable spring heat wave since 1886, and that warm spell occurred a full month later (April 16-24). In Chicago, last week’s high temperatures in the low 80’s are similar to Chicago’s average high in August (82°).
Daily record highs have been falling in droves across the region, with some remarkable occurrences. One weather station in Michigan hit 85°F, breaking the previous daily record high by an unheard of 32°, which is also 48° above average. Two stations recorded low temperatures that beat the previous record high, something that experienced weatherman Jeff Masters had never seen before. This record warmth is not confined to the United States. Several Canadian cities surpassed both their all-time March and April records this week, an amazing feat considering the vast differences between March and April during a normal spring.
NOAA recently declared this winter to be the 4th warmest on record for the contiguous United States. That sort of announcement might be expected in a warming world. But what about the relatively cold winters of 2009-2010 and 2010-2011, which featured historic blizzards in the Midwest and the East Coast? Florida had snow seven times in 2010! And while we Americans enjoyed a very mild winter this year, Europe endured its most frigid cold snap in decades. That sort of winter weather may seem counter-intuitive in a warming world; it’s the sort of weather columnist Thomas Freidman has in mind when he writes about “Global Weirding.”
NOAA reported today that this winter turned out to be the 4th warmest on record in the contiguous United States. That’s not surprising given how much the world has warmed over the past few decades. In fact, all of the seven warmest years in over 100 years of climate data have occurred since 1992, and over the past three decades, a warmer-than-average winter has been twice as likely as a cool one. These data are consistent with how scientists say global warming affects the weather. The risk of warm winters is increasing over time, but that doesn’t mean that cold winters disappear, similar to the way that loaded dice change the probability of a particular roll but don’t eliminate other possibilities.
A common analogy to explain the link between climate change and extreme weather is gambling with “loaded dice.” For people who aren’t the gambling type but love America’s pastime, perhaps Barry Bonds’ homerun statistics would be more enlightening, or at least more entertaining. A new video from the National Center for Atmospheric Research draws an analogy between a batter on steroids and the “doping” of the atmosphere with manmade CO2.
Extreme Weather and Climate Change
Understanding the Link, Managing the Risk
Updated December 2011
Thousands of record-breaking weather events worldwide bolster long-term trends of increasing heat waves, heavy precipitation, droughts and wildfires. A combination of observed trends, theoretical understanding of the climate system, and numerical modeling demonstrates that global warming is increasing the risk of these types of events today. Debates about whether single events are “caused” by climate change are illogical, but individual events offer important lessons about society’s vulnerabilities to climate change. Reducing the future risk of extreme weather requires reducing greenhouse gas emissions and adapting to changes that are already unavoidable.
Typically, climate change is described in terms of average changes in temperature or precipitation, but most of the social and economic costs associated with climate change will result from shifts in the frequency and severity of extreme events. This fact is illustrated by a large number of costly weather disasters in 2010, which tied 2005 as the warmest year globally since 1880. Incidentally, both years were noted for exceptionally damaging weather events, such as Hurricane Katrina in 2005 and the deadly Russian heat wave in 2010. Other remarkable events of 2010 include Pakistan’s biggest flood, Canada’s warmest year, and Southwest Australia’s driest year. 2011 continued in similar form, with “biblical” flooding in Australia, the second hottest summer in U.S. history, devastating drought and wildfires in Texas, New Mexico and Arizona as well as historic flooding in North Dakota, the Lower Mississippi and in the Northeast.
Munich Re, the world’s largest reinsurance company, has compiled global disaster for 1980-2010. In its analysis, 2010 had the second-largest (after 2007) number of recorded natural disasters and the fifth-greatest economic losses. Although there were far more deaths from geological disasters—almost entirely from the Haiti earthquake—more than 90 percent of all disasters and 65 percent of associated economic damages were weather and climate related (i.e. high winds, flooding, heavy snowfall, heat waves, droughts, wildfires). In all, 874 weather and climate-related disasters resulted in 68,000 deaths and $99 billion in damages worldwide in 2010.
The fact that 2010 was one of the warmest years on record as well as one of the most disastrous, begs the question: Is global warming causing more extreme weather? The short and simple answer is yes, at least for heat waves and heavy precipitation. But much of the public discussion of this relationship obscures the link behind a misplaced focus on causation of individual weather events. The questions we ask of science are critical: When we ask whether climate change “caused” a particular event, we pose a fundamentally unanswerable question (see Box 1). This fallacy assures that we will often fail to draw connections between individual weather events and climate change, leading us to disregard the real risks of more extreme weather due to global warming.
Climate change is defined by changes in mean climate conditions—that is, the average of hundreds or thousands events over the span of decades. Over the past 30 years, for example, any single weather event could be omitted or added to the record without altering the long-term trend in weather extremes and the statistical relationship between that trend and the rise in global temperatures. Hence, it is illogical to debate the direct climatological link between a single event and the long-term rise in the global average surface temperature.
Nonetheless, individual weather events offer important lessons about social and economic vulnerabilities to climate change. Dismissing an individual event as happenstance because scientists did not link it individually to climate change fosters a dangerously passive attitude toward rising climate risk. The uncertainty about future weather conditions and the illogic of attributing single events to global warming need not stand in the way of action to manage the rising risks associated with extreme weather. Indeed, such uncertainty is why risk managers exist – insurance companies, for example – and risk management is the correct framework for examining the link between global climate change and extreme weather.
An effective risk management framework accommodates uncertainty, takes advantage of learning opportunities to update understanding of risk, and probes today’s rare extreme events for useful information about how we should respond to rising risk. Risk management eschews futile attempts to forecast individual chaotic events and focuses on establishing long-term risk certainty; that is, an understanding of what types of risks are increasing and what can be done to minimize future damages. An understanding of the meaning of risk and how it relates to changes in the climate system is crucial to assessing vulnerability and planning for a future characterized by rising risk.
For more on the relationship between extreme weather and climate change, visit our Extreme Weather web page, where you'll find our extreme weather events map, along with other reports and C2ES resources.
 Karl, T. R., Meehl, G. A., Miller, C. D., Hassol, S. J., Waple, A. M., & Murray, W. L. (2008). Weather and Cliamte Extremes in a Changing Climate; Regions of Focus: North America, Hawaii, Caribbean, and U.S. Pacific Islands. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. Washington, D.C., USA: Department of Commerce, NOAA's National Climatic Data Center.
 BBC News. (2011, January 1). Australia's Queensland faces 'biblical' flood. Retrieved May 19, 2011, from http://bbc.in/fNzGgK; Associated Press. (2011, May 1). Federal fire crews bring expertist to huge TX fire. Retrieved May 19, 2011, from http://bit.ly/iz6JRs; Associated Press. (2011, June 16). Concern over human-caused blazes grows as wind-driven wildfires promp more evacuations. Retrieved June 22, 2011, from Washington Post: http://wapo.st/iWxirz; Sulzberger, A.G. (2011, June 26). In Minot, N.D., Flood Waters Stop Rising. Retrieved November 22, 2011, from New York Times: http://nyti.ms/ufT9jY; Doyle, R. (2011, September 8) U.S. sweltered through hottest summer in 75 years. Retrieved November 22, 2011, from USA Today: http://usat.ly/o73h4o; Robertson, C. (2011, May 15). Record Water for a Mississippi River City. Retrieved November 22, 2011, from New York Times: http://nyti.ms/lp0cTA; Freedman, A. (2011, September 12). Historic Flooding Recedes in Pennsylvania, New York; at least 15 dead. Retrieved November 22, 2011, From Washington Post: http://wapo.st/qvywOo
 Karl et al., Weather and Cliamte Extremes in a Changing Climate, Op. cit.