risk management

Accounting for scientific uncertainty in a dangerously warming world

Most people at some point develop a “Plan B” – in case their first choice of college doesn’t accept them, or it rains on the day of their planned outdoor party, or the deal for the house they wanted falls apart. The same principle applies for more dire situations, such as a city having plans in hand for an orderly evacuation in case of a large-scale disaster. We hope such an event will never happen, but the mayor had better be prepared in case it does.

In a commentary today in the scientific journal Nature Climate Change, three colleagues and I discuss the need for a “Plan B” for climate change: How will we cope with increasingly severe climate impacts if we are unsuccessful in limiting global warming to a chosen target?

In the 2009 Copenhagen climate accord, countries set a goal of limiting global warming to below 2 °C (3.6 °F) above the average global temperature of pre-industrial times. However, given that the planet has already warmed by 0.8 °C, additional warming is already locked into the system, and global greenhouse gas emissions continue to rise, this “Plan A” has become increasingly difficult and may become impossible to achieve if widespread emissions reductions do not begin within this decade. A maximum warming target is a necessary goal of climate policy, but what if our efforts fall short?

Some voices in the environmental community will feel that asking this question is ceding failure, but I disagree. Instead, it means admitting that we can’t perfectly foresee the future and that we need to be prepared for surprises. This is called risk management and everyone from parents, to mayors, to companies, to the U.S. military uses risk management every day to cope with uncertainty.

Extreme Weather

 

Extreme Weather Event Map: Click on any icon on the map above to see details on the extent of an extreme weather event between 1990 and 2012.

 

Extreme Weather Events Map

The events shown above are examples of four types of extreme weather that scientists say are becoming more frequent and intense because of climate change: extreme heat, drought, wildfires, and heavy precipitation. Individual events cannot be blamed on any single cause.  However, the long-term trends in these types of events demonstrate that extreme weather risk is rising as a result of climate change. Each new event is an opportunity to better understand our vulnerabilities and ways to cope with these rising risks. Examined together, these events also can help us evaluate the benefits of actions and policies aimed at reducing the emissions of heat-trapping gases that are warming the planet and “juicing up the weather”.

Here are two C2ES papers taking a closer look at the trends shown in the map and how we can respond:

 


Scientific American Series on Extreme Weather, Climate Change, and the Risks We Face

Published in three parts in June 2011, this series in Scientific American provides firsthand accounts of record-breaking weather events, insights into their links to climate change, and what can be done to manage the growing risks.  The articles were written by science journalist John Carey with support from C2ES.


 

Additional C2ES Resources

Find answers to some of the most frequently asked climate science questions and learn about the realities and misconceptions of climate change science.

Learn how Hurricane Sandy is a stark reminder of the rising risks of climate change.

See the latest on drought and climate change.

Learn more about extreme heat and climate change.

Keep up to date on current extreme weather events, climate change, and risk management.

Extreme Weather and Climate Change

Extreme Weather and Climate Change
Understanding the Link, Managing the Risk

Updated December 2011

by Daniel G. Huber and Jay Gulledge, Ph.D.

Download the paper (pdf)

Press release

Listen to the press briefing

 

Executive Summary:

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.

Introduction:

Box 1. Why can’t scientists say whether climate change “caused” a given weather event?

Climate is the average of many weather events over of a span of years. By definition, therefore, an isolated event lacks useful information about climate trends. Consider a hypothetical example: Prior to any change in the climate, there was one category 5 hurricane per year, but after the climate warmed for some decades, there were two category 5 hurricanes per year. In a given year, which of the two hurricanes was caused by climate change? Since the two events are indistinguishable, this question is nonsense. It is not the occurrence of either of the two events that matters. The two events together – or more accurately, the average of two events per year – define the change in the climate.

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.[1] This fact is illustrated by a large number of costly weather disasters in 2010, which tied 2005 as the warmest year globally since 1880.[2] 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.[3]

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.[4]  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.[5] 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.

What about climate change and tornadoes?

Scientists are unsure if tornadoes will become stronger or more frequent, but with increased temperatures changing the weather in unexpected ways, the risk is real that tornado outbreaks will become more damaging in the future.  The lack of certainty in the state of the science does not equate with a lack of risk, since risk is based on possibility.  The lack of scientific consensus is a risk factor itself, and we must prepare for a future that could possibly include increased tornado damage.

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.

Endnotes


[1] 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.

[2] National Climatic Data Center. (2010, December). State of the Climate Global Analysis: Annual 2010. Retrieved May 19, 2011, from http://1.usa.gov/fxdFai

[3] 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

[4] Munich Re. (2011, February). Topics Geo Natural catastrophes 2010: Analyses, assessments, positions. Retrieved May 19, 2011, from http://bit.ly/i5zbut

[5] Karl et al., Weather and Cliamte Extremes in a Changing Climate, Op. cit.

 

 

Daniel Huber
Jay Gulledge
0

Adding More Weather Risk to the Climate System

This op-ed appeared in CQ Researcher.

September 2011

By Jay Gulledge

The risk of extreme weather is rising because of climate change. In the United States, long-term trends show an increasing number of heat waves and heavy downpours and longer, more destructive droughts and wildfires. Climate models simulate these same trends when scientists examine the effects of increases in global warming’s main ingredient – greenhouse gases.

Risk is the best way to understand the link between climate change and extreme weather. Just as smoking and high cholesterol are risk factors for heart disease, natural cycles and global warming are risk factors for extreme weather. This year’s weather impacts have been particularly severe because multiple risk factors are aligned: A long, intense La Nina – a temporary cool period in the equatorial Pacific Ocean that is associated with extreme temperatures, droughts, and flooding in other parts of the world – is occurring at the same time we are experiencing the warmest decade in at least 130 years. The big difference between these risk factors is that natural cycles come and go, whereas global warming increases over time as atmospheric greenhouse gases grow, constantly adding more weather risk to the climate system.

Escalating weather impacts are cutting deeply into the economy. The world’s largest re-insurance company says the number of weather- and climate-related disasters worldwide more than doubled over the past 30 years. Economic losses attributable to weather variability run $485 billion annually. Several multi-billion-dollar events have occurred this year, including Texas’ worst single-year drought, the Mississippi floods, and Hurricane Irene, which is expected to rank among the ten costliest hurricanes in U.S. history.  As the weather becomes more volatile, economic risk will continue to grow.

As recent weather events teach us more and more about our vulnerabilities, the taxpayer-funded National Flood Insurance Program is already $18 billion in debt. Because most of the damage from Hurricane Irene is not privately insured, this financially-strapped program is under pressure once again. And the Federal Emergency Management Agency (FEMA) is running out of money to respond to disasters, even as Congress bickers over how to refill the coffers.

Flood insurance is the federal government’s second-largest fiscal liability after social security. Ignoring rising climate risk will only allow these hidden costs to suck up more taxpayer money. Reducing greenhouse gas emissions and adapting to changes already under way bends down the risk curve, just as exercise and medical insurance lower health risks. If we don’t take these steps, our children and grandchildren will inherit a more dangerous and costlier climate.

Jay Gulledge is the Senior Scientist and Director of the Science and Impacts Program at the Pew Center on Global Climate Change.

by Jay Gulledge--Published in CQ Researcher
Syndicate content