August 18, 2010

Climate Risks: Lessons from 2010’s Extreme Weather

This post was originally published yesterday by the Climate Compass blog at the Pew Center on Global Climate Change where Dr. Jay Gulledge is Senior Scientist and Director of the Science and Impacts Program at the Pew Center on Global Climate Change. He is also a Non-Resident Senior Fellow at the Center for a New American Security.

Last fall I posted a blog about the unusual number and severity of extreme weather events that have been striking around the globe for the past several years. That entry focused on the alternating severe drought and heavy flooding in Atlanta in 2007-2009 as an example of the roller coaster ride that climate change is likely to be. As every dutiful scientist does, I stopped short of blaming those individual weather events on global warming, but I am also careful to point out that it is scientifically unsound to claim that the confluence of extreme weather events in recent years is not associated with global warming; I’ll return to this question later.

Tempestuous 2010

The weather of 2010 continues the chaos of recent years. In the past six months, the American Red Cross says it “has responded to nearly 30 larger disasters in 21 [U.S.] states and territories. Floods, tornadoes and severe weather have destroyed homes and uprooted lives …” Severe flooding struck New England in March, Nashville in May, and Arkansas and Oklahoma in June.

Nearly the entire northern hemisphere is experiencing a massive heat wave this summer. Back in February, heavy snowfall in D.C. prompted some politicians to decry global warming, but those voices are now silent in the searing heat that has gripped much of the world this summer. The first half of 2010 has been the warmest January-July period in the global temperature record, stretching back to 1880. I would be the first to question the significance of this single-year observation, but it fits perfectly into a multiple-decade pattern in which each year between 2000 and 2009 was warmer than the average temperature of the 1990s, and every year in the 1990s was warmer than the average temperature for the 1980s.

As extreme as the weather has been in the U.S. this year, things are much worse in other countries that are of great interest to the United States:  Pakistan and Russia. (Severe flooding in China is worthy of discussion as well, but I’ll limit my focus in this post to Pakistan and Russia.)

The current flooding in Pakistan is the worst in that country’s history, with two million people homeless, 20 million affected, more than a million acres of croplands flooded, and signs of an incipient cholera epidemic. Six million people are without assistance in severely affected areas. The UN calls this crisis the world’s worst humanitarian disaster in recent history. To make matters worse, additional flooding is in the forecast, as the monsoon season continues through next month.

Meanwhile, Russia is locked in the worst heat wave and drought in its documented history, with unprecedented high temperatures in Moscow and hundreds of wildfires burning out of control. The combination of extreme heat and thick smoke and smog from the fires doubled the city’s death rate at the peak of the heat wave last week. The drought and fires have destroyed a quarter of Russia’s crops, prompting the government to ban grain exports for the rest of this year in hopes of keeping domestic food prices under control. Since Russia is one of the biggest grain exporters, this move contributed to a spike in the price of wheat on the global market.

The Science

One might think that too much rain in Pakistan would have nothing to do with too little rain in Russia, but two expert analyses by CNN meteorologist Brandon Miller and Weather Underground meteorologist Dr. Jeff Masters find that the two are connected. The Russian heat wave is associated with an intense dome of high atmospheric pressure that has settled in over Eastern Europe. This dome is so immovable that it is blocking the flow of the jet stream, which typically determines where mid-latitude storms drop their rains. A similar “blocking high” was in place over Western Europe during the extremely deadly 2003 European heat wave. The block over Russia forced the jet stream to dive far southward, carrying with it a great deal of moisture that normally would have watered Russia’s substantial wheat crop. Instead, that rain fell in northern Pakistan, combining with the already abundant rainfall normally associated with the Asian Monsoon this time of year. The combination of the two was just too much, so while Russia’s crops withered and burned, Pakistan’s crops drowned.

Returning to the question everyone wants answered: What can we say about the connection between these events and climate change? As usual, there is no definitive answer about these specific events, but direct observations show that extreme weather events have become more frequent in the past half-century, and in the extreme cases that have been studied, the mechanisms are those that one would expect from global warming. At the most basic level, more droughts and heat waves are expected because of hotter, longer-lasting high pressure systems that dry out the land, as witnessed in Russia. On the other hand, more floods are expected because hotter air evaporates more water from the surface and holds more moisture. When the conditions are right, that moisture is released, creating a deluge, as witnessed in Pakistan. The same basic phenomenon was behind the unusually heavy snowstorms that hit the U.S. East Coast this winter.

More specifically, modeling experiments performed by British scientists indicated that the risk of extreme European heat waves like the one in 2003 has at least doubled as a result of human-induced global warming. The same models predicted that continued greenhouse-gas emissions would make similar heat waves commonplace in Europe by the middle of this century. Independent modeling experiments by American climate scientists found that strong blocking highs and associated long, extreme heat waves occurred more frequently in models with elevated greenhouse gas concentrations. (An accessible version of the latter work is available in a report published by the Pew Center in 2007.)

So 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.

Winners and Losers?

Economists and security analysts frequently argue that Russia is likely to be a climate change “winner,” since warmer temperatures could reduce heating fuel consumption, lengthen the agricultural growing season, and open up transportation routes and access to mineral and energy deposits in the Arctic. But these types of analyses inevitably focus on a few simplistic variables, while neglecting a plethora of more complex and likely negative impacts. It seems clear that Russia will not benefit from warm weather this year, and if this type of event were to become common in future decades, it is hard to see Russia being climate-change winner, even if it is rich on oil and gas money. Moreover, Russia is fighting an ongoing extremist insurgency at home that has ties with both Al Qaeda and the Taliban in Afghanistan and Pakistan. Does Russia “win” if the Taliban and other hard-line extremists step in to fill the void left by an ineffectual government and international aid response to the floods in Pakistan?

It’s time to put to rest the overly simplistic notion that there will be clear winners and losers in a warmer world. I had the privilege of working with top-flight national security experts on a report published by the Center for a New American Security and the Center for Strategic and International Studies in 2007, called The Age of Consequences:  The Foreign Policy and National Security Implications of Climate Change. In the executive summary, we wrote:

“A few countries may benefit from climate change in the short term, but there will be no ‘winners.’ Any location on Earth is potentially vulnerable to the cascading and reinforcing negative effects of global climate change. While growing seasons might lengthen in some areas, or frozen seaways might open to new maritime traffic in others, the negative offsetting consequences—such as a collapse of ocean systems and their fisheries—could easily negate any perceived local or national advantages. Unchecked global climate change will disrupt a dynamic ecological equilibrium in ways that are difficult to predict. The new ecosystem is likely to be unstable and in continual flux for decades or longer. Today’s ‘winner’ could be tomorrow’s big-time loser.”

Remarkably, Russian President Medvedev seems to get the point. Speaking to an international gathering, in front of TV cameras, the president was forthright: “Practically everything is burning. The weather is anomalously hot. What's happening with the planet's climate right now needs to be a wake-up call to all of us, meaning all heads of state, all heads of social organizations, in order to take a more energetic approach to countering the global changes to the climate.”

The misleading notion of winners and losers encourages colder, richer countries to hold out on international agreements to cut greenhouse gas emissions. One can only hope that world leaders will begin to see the hubris in the “winners and losers” paradigm. If we continue to delay reductions of greenhouse gas emissions, there is a serious risk that we will all be losers.