How Should We Think About Extreme Weather Events?

The rough weather of 2010 teaches us that climate change is risky business.

Recently, I posted a blog discussing the possible link between global climate change and two related extreme weather events: the heat wave in Russia and historic flooding in Pakistan. Although there is no method to definitively attribute any single event to climate change, based on documented trends in extreme weather events and research showing that specific types of meteorological phenomena are more common in a greenhouse-warmed world, I said:

“It is reasonable to conclude that, in aggregate, the documented increase in extreme events is partially a climate response to global warming, and that global warming has increased the risk of extreme events like those in Russia and Pakistan. On the other hand, there is no scientific basis for arguing that these events have nothing to do with global warming.”

That’s as far as the science permits me to go with this question. We simply cannot know whether any particular weather event was “caused” by climate change. In recent weeks, however, the media have done their all-too-common “he said-she said” routine of finding one source who says the extreme weather of 2010 is because of climate change and another who says it’s not. This is a meaningless argument that distracts us from what we should be thinking about, which is what these events can teach us about our vulnerabilities to climate change.

Global Warming Makes Weather More Extreme

The public has the unfortunate misperception that scientists generally disagree about the reality and causes of global climate change. Scientists may disagree on some details, like individual weather events, but they have an astonishing level of consensus on the basics: The planet is warming and human activities are primarily responsible for the warming that has occurred since the mid-20th century. There is also broad agreement that a warmer climate translates into more extreme weather events.

To illustrate, consider the conclusions of the Physical Sciences Division of NOAA’s Earth System Research Lab in Boulder, Colorado. This analysis concluded that the Russian heat wave was primarily a natural event. But it also says something much more instructive:

“As we learn from our 2010 experience what a sustained heat wave of +5°C to+10°C implies for human health, water resources, and agricultural productivity, a more meaningful appreciation for the potential consequences of the projected climate changes will emerge. It is clear that the random occurrence of a summertime block in the presence of the projected changes in future surface temperature would produce heat waves materially more severe than the 2010 event.”

I could not agree more. There are important lessons to be learned from the extreme weather events we are experiencing. But the over-emphasis on the cause of a particular event distracts us from the important point that climate change is just getting underway. The extent to which global warming to date has affected extreme weather will pale in comparison to the future if we continue to let greenhouse gases (GHGs) grow in the atmosphere.

Taking Lessons about Risk

Science is not a crystal ball, but it offers powerful tools for assessing the risks of climate change. The questions we ask of science are critical. When we ask whether climate change “caused” a particular event, we pose a fundamentally unanswerable question. This fallacy assures that we will fail to draw firm connections between individual weather events and climate change, tempting us to disregard the very real risks of more extreme weather events because of climate change.

A more appropriate question is whether global warming loads the dice in favor of certain types of events. When current weather events align with what the science tells us to expect from climate change, we can then ask what those events reveal about our vulnerabilities. Whether the event we are learning from is a consequence of climate change is irrelevant.

Rather than argue endlessly about cause and effect, we should be focusing on how vulnerable we are to those types of events and thinking about how we can manage the associated risks. What should we be doing to minimize the damage and costs of the rising risk of similar events in the future? These are critically important questions that risk managers use to cope with uncertainty.

For example, previous research shows that the historic heat wave that struck Central Europe in 2003 was twice as likely to occur with current greenhouse-gas concentrations as compared to pre-industrial concentrations. The Russian heat wave has a similar profile of unprecedented extreme heat under a long-lasting, stationary high pressure system, and it occurred in a location that is susceptible to wild variations in extreme temperatures in a warming world. It doesn’t matter whether the 2010 event is a consequence of climate change; we know the consequences were severe, and climate change increases the risk that even worse events will occur in the future.

Some Lessons to Date

For example, before the unprecedented European heat wave of 2003, we had no idea that a heat wave could kill 14,000 people in the fifth richest country in the world, France. Similarly, before Hurricane Katrina struck New Orleans, we did not know that a natural disaster could literally shut down a major American city and strand tens of thousands of helpless citizens without clean water, electricity, and communication to the outside world for days and weeks. It doesn’t matter whether Katrina was a product of climate change. It matters that a warmer world brings the risk of more powerful hurricanes, and Katrina has taught us how vulnerable we can be, even in the world’s richest country.

We also learned this year that downtown Nashville can be completely inundated by flood waters within hours, that a heat wave can kill thousands of cattle in Kansas, and that well-heeled residents of suburban Washington, DC, can be without power, repeatedly, for days at a time because of intense summer thunderstorms and winter snowstorms (See my earlier post on why the heavy snow that hit Washington this past winter is actually consistent with what we expect of climate change).

Other recent events are teaching us about the national and international security risks of climate change. The Russian drought affected global food prices, elevating the risk of food riots and instability around the world, similar to the worldwide events of 2008. Predictions of the security risks from climate change are playing out before our eyes in Pakistan, a key ally to the United State’s effort to stamp out international terrorism. Millions of people are displaced from their homes by the unprecedented flooding in Pakistan. One of the hardest hit areas is the Swat Valley, where the Pakistani government has been battling Taliban insurgents at the behest of the United States.

These circumstances validate the concept of climate change as a security threat multiplier, as theorized by a board of retired three- and four-star military officers a few years ago.

The Bottom Line

Given the uncertainties and the associated risks, it does not make sense to focus on whether current events are supercharged by climate change. It does make sense, however, to take lessons from them about our current vulnerabilities and the risks involved in letting the climate continue to warm.

Jay Gulledge is Senior Scientist and Director of the Science and Impacts Program