Is climate change a factor in severe floods and droughts? | St. Louis Public Radio

Is climate change a factor in severe floods and droughts?

Dec 5, 2011

This article first appeared in the St. Louis Beacon, Dec. 5, 2012 - WASHINGTON - From historic floods in the Midwest to destructive clusters of tornadoes in the mid-South to drought-related fires sweeping across Texas, the number of officially declared U.S. disasters reached a new record this year.

While those natural disasters in the United States play only a small role in the World Meterological Organization's (WMO) report on extreme weather events in 2011, there is a tendency to try to link the underlying weather patterns to changes in the global climate.

At the height of last summer's Missouri River flooding, for example, liberal Sen. Tom Harkin, D-Iowa -- arguing that climate change is "indisputable" -- urged the Army Corps of Engineers to re-evaluate its river management manual to reflect changing patterns of precipitation that seem to be related to climate change.

At a Senate hearing last month on Missouri River flooding, Sen. Max Baucus, D-Mont., fretted that "there is going to be increased volatility in weather cycles" due to climate change and suggested that the Corps may need to change its calculations of the threat of flooding in various parts of the Big Muddy's basin.

Which raises the question: Is it possible to link a specific flood or drought event to climate change? While many climate experts predict increases in weather-cycle volatility, most of them are also careful in qualifying that it is not possible to relate a single "extreme event" to climate change.

Possible links between global climate change and extreme weather patterns have been discussed at the 17th annual United Nations climate conference, held in Durban, South Africa. There, delegates discussed how to raise billions of dollars for a "green climate fund" to help poor countries cope with global warming, and weighed a new report that Arctic sea ice has receded to a record low volume.

While the studies of some interest groups asserted that climate change would exacerbate weather-related disasters, a report by the influential Intergovernmental Panel on Climate Change (IPCC) on extreme events and climate change said it would be difficult to blame specific extreme weather events (such as a single flood or drought) to climate change that is exacerbated by human activity.

"Attribution of single extreme events to anthropogenic [human-influenced] climate change is challenging," said a summary of the report, which was based on a consensus of international scientists who analyzed the published research.

Even so, the study found more general patterns that indicate that human activity -- mainly greenhouse gas emissions -- has not only played a role in global warming but also has led to a general increase in some extreme weather an climate events.

For example, the IPCC summary said that "projected precipitation and temperature changes imply possible changes in floods, although overall there is low confidence in projections of changes in fluvial [river] floods," the report said.

It added: "There is medium confidence . . . that projected increases in heavy rainfall would contribute to increases in local flooding, in some catchments or regions."

As Disasters Increase, Experts Seek Explanations

There is no doubt that the number of U.S. federal disaster declarations has increased in the past couple of years, but there is disagreement over whether that spike relates as much to more extreme weather as it does to the politics of declaring disasters.

The Federal Emergency Management Agency (FEMA) reports that, so far this year, there have been 97 "federal disaster declarations" as well as 28 lesser "emergency declarations" and 113 "fire management assistance declarations."

According to FEMA statistics, that is the largest number of major disaster declarations in U.S. history, approached only by last year's total of 81 declarations. In the decade before that, the number of disaster declarations ranged from a low of 45 (in 2000 and 2001) to a high of 75 (in 2008).

At a Senate hearing in July, FEMA Deputy Administrator Richard Serino said that a big part of the reason for the rise in disaster declarations is that "we have had some record-setting weather ... a high number of tornadoes and record high flood stages on the Mississippi and Missouri rivers. So we're seeing disasters in large number mainly because of shifts in some of the weather patterns."

While there is disagreement about whether climate change has anything to do with such temporary shifts in weather patterns, few if any atmospheric scientists saw a link between last spring's deadly clusters of tornadoes in the mid-South -- including the twister that destroyed much of Joplin, Mo. -- and global climate trends.

Ernest M. Agee, who heads a leading tornado research group at Purdue University in Indiana, told the Beacon that this spring's above-average spate of tornadoes may relate to the La Nina cycle rather than to global climate change.

A cyclical drop in temperatures in the Pacific Ocean, La Nina tends to last five or six months and repeat every three to five years. This spring, such a pattern is forcing the North American jet stream eastward and southward, which alters prevailing winds. The jet stream's high, cool air then pulls upward more humid, warmer air -- creating the "super cells" of thunderstorms.

"But [the cause] is not all La Nina," Agee said. "It's very normal to have abnormal weather." He said that global warming trends would lead to more heated moisture, but any direct connection to climate patterns is unclear. "You have these [tornado] episodes, and then you don't have them. They hit in rural areas, and then they don't."

Studies Don't Prove Link to Extreme Weather

Skeptics of the human-activity causes of climate change like to say that, "the climate is always changing" as a result of the Earth's natural cycles. And, to be sure, "paleo-climate" studies have shown that there always have been extreme weather events -- floods, droughts, intense cold and heat -- and that the climate changes over time.

"It's difficult for people to resist the temptation to try to draw weather events that are taking place this week or this year to the global warming argument," said Sen. James Inhofe, R-Okla., who is one of Congress' most outspoken climate-change skeptics.

However, most scientists who examine the data have concluded that the rate of global warming over the last half century is unusual. "The conclusion of the scientific community is clearly that the climate is changing rapidly -- not only in temperature but in other ways as well -- and that human beings are the major factor driving it," renowned botanist Peter Raven, president emeritus of the Missouri Botanical Garden, told the Beacon in October.

Several new reports, most of them issued over the past couple of weeks at or before the Durban climate conference, have added fuel to the argument for climate change, and some tried to draw general links between that phenomenon and trends towards extreme weather events. A few examples:

-- The 2011 "Arctic Report Card" compiled by scientists from 14 countries, reported "record-setting changes ... occurring throughout the Arctic environmental system."

"Given the projection of continued global warming, it is very likely that major Arctic changes will continue in years to come, with increasing climatic, biological and social impacts," the report said.

Update 11:59 a.m. Monday -- The Global Carbon Project reported on Sunday that global emissions of carbon dioxide from the burning of coal, gas and other fossil fuels increased by 5.9 percent last year -- the largest percentage increase since 2003 and possibly the greatest tonnage increase of such emissions in any year since the Industrial Revolution.

This year's carbon report, compiled by an international group of scientists, is considered important because it showed a reversal of the global recession's apparent downward trend in emissions, reflected in the 1.4 percent drop in 2009. end new information

-- Information released Thursday by a British risk-analysis firm Maplecroft showed that more than half of all carbon pollution released into the atmosphere comes from five countries -- with China topping the list, followed by the United States, India, Russia and Japan.

A related Maplecroft survey concluded that the fastest-growing nations are among the most vulnerable to climate change. Other than California and some other coastal regions (classified as "medium risk"), the continental United States was rated as "low risk." from the impacts of "climate related natural hazards, including sea level rise."

-- The nonprofit relief organization Oxfam International reported in Durban that droughts, floods and other "extreme weather events" worldwide are leading to famines.

While conceding that "it is difficult to attribute a specific weather-related disaster to climate change," Oxfam's statement warned that "the frequency and severity of extreme weather events such as those seen this year is set to increase due to climate change."

-- The IPCC scientific assessment predicted that some forms of extreme weather would likely increase in coming decades as more greenhouse gases accumulate in the atmosphere.

However, the report cautioned that experts cannot attribute a specific flood or drought to climate change, and at the moment cannot accurately predict the impact of global warming on such events as tropical cyclones. While worldwide damage from natural disasters has increased in recent years, the report said that might have more to do with greater exposure of property and people to weather risks than it does to climate change.

But IPCC scientists and others are more positive about future trends -- especially the predicted rise in sea levels as ice fields melt. Governments around the world -- especially those with coastal areas that are vulnerable to the expected rise in sea levels -- are taking steps to try to limit the impact of climate-change trends.

"The conservative estimate is that sea levels will rise by about five feet during the course of this century," said Raven, who served on a National Research Council panel that called earlier this year -- in the final report of the America's Climate Choices project -- for more action to try to limit the extent of climate change and prepare to adapt to its impacts.

"The government of Vietnam estimates that it will lose one-third of its farmland during the course of this century," he said. "The government of China, which has three large industrial zones along its east coast, projects that 30 percent of each of those will be lost to sea-level rise during the rest of this century. Those countries are taking steps to deal with it."

Raven predicted that changing climate would lead to "very serious problems with agriculture" in many countries. He added: "It means that people in Florida and a lot of other places ought to be dealing with that, not building in low elevations and just thinking about where land should be traded, and putting up various kinds of barriers."

Efforts to Predict Long-term Risks in the U.s.

In this country, the U.S. National Climate Assessment (NCA) is in the midst of integrating and interpreting the findings of the federal research program on global climate change over the last few years, in an effort to predict its potential impact.

The most recent NCA report, in 2009, described increases in average temperatures in the Midwest and predicted that "the likely increase in precipitation in winter and spring, more heavy downpours, and greater evaporation in summer would lead to more periods of both floods and water deficits."

"Heavy downpours are now twice as frequent as they were a century ago. Both summer and winter precipitation have been above average for the last three decades, the wettest period in a century," the report said. Written before this year's record flooding on both the upper Missouri and lower Mississippi rivers, the report said "the Midwest has experienced two record-breaking floods in the past 15 years."

The Midwest flooding and Texas drought are also mentioned in this week's World Meterological Organization report, which said that this year, so far, is tied as the 10th warmest year since record keeping began in 1850. The report also said the volume of Arctic sea ice (an indicator of the planet's warmth), had shrunk to a record low of 4.3 million square kilometers.

Without claiming any links to global climate trends, the report commented on the "year of extremes in the United States, with 14 separate weather/climate events which caused losses of $1 billion or more each."

In contrast to the "extreme drought [that] affected parts of the southern United States and adjacent parts of northern Mexico," the reported noted that "many northern and central parts of the United States experienced heavy rain and flooding in 2011. The January-October period was the wettest on record for several north-eastern states and for the north-east region as a whole, with precipitation totals widely 30-50% above normal."

The report went on to say that "spring and early summer were extremely wet in many central areas, particularly the Ohio Valley and the upper Midwest of the United States .... The heavy spring rains, combined with the melting of a heavy winter snowpack in northern areas, caused major downstream flooding during May and June. Parts of the Mississippi River experienced the worst floods since 1933, and there was also major flooding in the Missouri River and several Canadian rivers."

New Efforts to Draw Attention to Climate Change

While climate change remains a pressing issue for many of the developing nations who sent delegates to the conference in Durban, the issue has faded in the United States and other developed countries hit by the economic downturn that has dampened enthusiasm for any measures -- such as caps on carbon dioxide emissions -- that could slow industrial development and cost jobs.

In 2009, about two dozen members of Congress attended the Copenhagen climate conference, where initial high hopes for a lasting accord ended in acrimony. This year, no U.S. senators or congressmen were planning to take part.

That is partly because so many U.S. lawmakers are skeptical about climate change and the impact of greenhouse gas emissions. And it also relates to the dampened expectations for the Durban talks.

While no binding deal was worked out in Copenhagen, the non-binding "Copenhagen Accord" appeared to commit major countries to some sort of emissions-reduction efforts, whether actual reductions or combinations of emissions-cutting policies and reductions in emissions intensity. Last year's climate meeting, in Cancun, Mexico, formalized that accord in what are called the "Cancun Agreements," and the Durban meeting is expected to flesh out many of the details in that sketchy document.

The U.S. Department of State is represented at the Durban talks by special climate envoy Todd Stern and other diplomats, who have made no commitments but are being urged by U.S. environmental groups and international organizations to at least signal the nation's intention to work toward a binding climate pact within nine years.

But the political situation in Congress appears likely to block any effort to negotiate and ratify a binding treaty that would commit the United States to capping greenhouse gas emissions. That's why a new coalition, called the Climate Ethics Campaign , was launched last week, with the goal of convincing politicians that they have an ethical duty to limit greenhouse gas emissions.

At a news conference this week, U.S. Sen. Barbara Boxer, D-Calif., the liberal chair of the Senate Environment and Public Works Committee, told the group that Congress is unlikely to act on climate-change issues unless there is more political pressure for action.

"To take it to the next step, we need a grassroots movement that is huge," Boxer said.