The recent weather events making news across America and across the globe do indeed give us all reason to pause. Certainly there have been recent, unusual, and in some cases tragically destructive, weather patterns, but no unanimous consensus is possible as to whether the changes are to some degree a cyclical event or a total de-linkage from the past. Likewise there never will be consensus as to how much of the changing patterns are attributable to human activities. However, we as an industry—and as a country—need to thoughtfully plan for an energy-efficient, carbon-constrained and climate-focused future. Utilizing the premier fuel that is natural gas should be a cornerstone to any such energy plan.

AGA has long understood the importance of balancing the need to meet increasing energy demands with an awareness of our environmental stewardship. Our member utilities and their customers have long supported efforts that encourage conservation and efficiency and the responsible development of America’s abundant natural gas resources.

That said, the wide-ranging debate over climate change, while taking into account the concerns of the environmental community, must also allow for reasonable input from industries likely to be affected by any resulting environmental legislation or regulations.

This is all the more reason to promote the direct use of natural gas in America’s homes and business. Not only is natural domestically abundant—meaning it can meet our growing energy needs right now—but also it is the cleanest and most efficient of the fossil fuels. In fact from the wellhead to the burner tip, natural gas loses only about 10 percent of its useable energy. Even when used to generate electricity, natural gas is cleaner than other fossil fuels and it can provide reliable baseload power, unlike other clean energy forms such as wind and solar, which are more intermittent in nature.

These attributes only highlight the important, and intelligent, role that natural gas plays in providing reliable and low-carbon energy.

One intense heat wave alone or one devastating flood by itself cannot be attributed to global warming. But when we look at the extreme weather occurring around the world this year, an undeniable pattern emerges: weather events are becoming more intense and severe. This trend is precisely what scientists have identified as a key indicator of global warming.

Scientists have known for years that extremity is the hallmark of climate change. It can take the form of extreme rain, extreme drought, and even extreme snowstorms.

In the past few months, we have seen the power of extreme heat. We just experienced the hottest 6 months on record globally, and many American cities have set all time records this summer. Last decade was the hottest decade on record, surpassing the 1990s, which was the previous record holder.

As Tom Peterson, Chief Scientist for NOAA’s National Climatic Data Center said recently: “We’re getting a dramatic taste of the kind of weather we are on course to bequeath to our grandchildren.”

Most Americans don’t want to stay on this dangerous course; they want to confront global warming. A recent poll conducted by Joel Benenson for NRDC’s Action Fund shows that 60 percent of voters want the government to regulate greenhouse gases.

But voter support isn’t the only force in politics. The oil and gas industry spent $174 million on lobbying the government in 2009. It already spent another $75 million in the first six months of this year. A sizable chunk of that money, including millions from Charles and David Koch, went to think tanks that manufactured doubts about climate science—science which researchers at the National Academy of Sciences, NOAA, the Pentagon, the CIA, and countless other nonpartisan institutions had already reached consensus on.

Too often, the media reports the issue like a contest: who won the skirmish over the so-called Climategate—the scientists or the deniers? But the stakes are far too high to treat this like a sporting event. This is an environmental and economic crisis, and I believe the facts and the reality of extreme weather will ultimately prevail over the deep pockets and self interest of a handful of polluters.

(These comments are from Andreas Muenchow, physical ocean science and engineering professor at the University of Delaware. He recently testified in front of the House Global Warming Committee on this issue.)

Neither climate nor weather is linear, but this neither makes them unpredictable nor chaotic. The simple harmonic pendulum is the essence of a linear system with clear cause and effect relations. Oscillations are predictable as long as the initial forcing is small. Furthermore, a linear trend will show the pendulum to slow down due to friction. Corrections are straightforward. Unfortunately, climate is not a simple, harmonic, or linear system. While this does not make it unpredictable or chaotic, it means that our “common sense” and loose talk of “totality of events” can easily fool us. We know that CO2 emissions for the last 150 years changed global temperatures. We also know that our current climate system has been very stable over the last 10,000 years. What we do not yet know is how small or how large a perturbations the last 150 years have been. If the pendulum is forced too much, if the spring is stretched too far, the system will find another stable state by breaking. Climate dynamics can find an adjustment less tuned to the areas where people presently live. This is what “tipping points” are about. Only numerical experimentation with the best physics and models will suggest how close to a different stable climate state we are. The IPCC process is one way to do so.

Ice cores from Greenland contain air bubbles 100,000 years old, which clearly demonstrate that our present climate state is the “anomaly of quiet” in terms of temperature fluctuations. The absence of large fluctuations for about 10,000 years made agriculture and advanced civilizations possible. The ice cores show that abrupt climate change has happened and may happen again, not this election cycle, but it is one possibility perhaps as likely as the possibility that climate change is mundane, linear, and follows trends that we can easily correct or mitigate later. Both are excellent hypotheses.

For scientists, these are exciting times as we conduct a massive, global experiment to see how much CO2 we can add to the atmosphere to perhaps find a different climate state. Dr. Terry Joyce, Senior Scientist at Woods Hole Oceanographic Institution once said: “I’m in the dark as to how close to an edge or transition to a new ocean and climate regime we might be. But I know which way we are walking. We are walking toward the cliff.” I agree with this sentiment, but add that we do not know if this cliff is a 1000 feet fall or a 2 feet step. Can we affort to wait until we know for sure? As a scientist I do not care. As a citizen, however, I think the time to act responsibly is now.

Climate change certainly has the potential to contribute to unwanted weather changes, but scientific research has yet to tie specific extreme weather events to anthropogenic warming. There have been numerous studies looking at trends in natural disasters and disaster-induced losses, and they have consistently failed to tie any such trend to human-induced warming. The latest of these, forthcoming in the Bulletin of the American Meteorological Society concluded: "Analyses show that although economic losses from weather related hazards have increased, anthropogenic climate change so far did not have a significant impact on losses from natural disasters."

Trying to link climate change to extreme weather events is risky. Pushing scientifically unsubstantiated claims about natural disasters undermines the credibility of those calling for action on climate change. It also diverts attention from those measures that can be taken now to enhance societal resiliancy and protect vulnerable communities from natural disasters here and now.

There is a strong case to be made for action on climate change, but it is not based on sensational claims about extreme weather.

Just because a doctor confronted with a patient's cancer can't definitively identify its cause - even though the patient is a regular smoker and the likely connection is obvious - it would be wrong for the doctor not to try curing the patient's disease or, even worse, refuse to treat the symptoms.

The same should hold true for climate change.

While we cannot say that any particular climate event like the destructive floods in Pakistan, unrelenting drought in the African Sahel, or the killer heat wave in Russia is definitively caused by climate change, these events are consistent with scientific predictions
of our climate change ailment and, critically, they are symptoms that need to be treated urgently.

For a child standing on a tiny island of land amid the floods in Pakistan, or a farmer in the African Sahel trying to scratch our an existence from parched land, or a Russian jumping into a river to cool off in the midst of the country's record setting heat-wave, the "future"
of a changed climate is already here. And this of course, is only the beginning.

Urgent action is needed in order to avoid the worst case scenarios. But since we face at least several decades of harmful warming already baked in the cake, we can't just rely on emissions-reduction strategies, as sorely needed as they are for coming decades. If we've learned anything from this year's extreme weather, it's that we need to prepare for the
consequences of climate change quickly and bolster our resilience to face it now.

From Oxfam's work in the poorest countries around the world and some of the poorest parts of the United State, we have seen that the consequences of climate events are not just about the physical impacts, but also the way in which those impacs interact with economic and social conditions. Entrenched poverty makes people more vulnerable to disasters, which can then in turn amplify economic and social instability and even conflict.

As a result, as the unfolding events around the world show, not preparing for the changing climate could result in substantial costs in human, economic and security terms. But by investing in global climate readiness strategies, we can help vulnerable communities become stronger and more prepared and resilient in the face of climate change.

This should include strategies from planting drought-resistant seeds to building coastal tree barriers and raised homes to fight floods (and many of these same strategies are highly relevant in the United States). In Pakistan, Oxfam and others have succeeded in saving many lives during the floods with early warning systems and community disaster response programs.

Acting now to put climate readiness in place can also save $7 for every dollar spent, according to US government and World Bank estimates for disaster prevention. And with these kinds of investments, we can also drive global economic growth. With support, communities in developing countries can invest in a variety of cost-effective projects that help
them overcome poverty in the long term. And around the world, including in the US, this investment can spur the development of water-saving and other technologies.

Scientists are hard at work to understand the link between climate change and this summer's violent weather events. But we policy wonks mustn't sit back and watch idly until some even more pointed "ah-ha" moment comes. We need to take action today, and it isn't just the right
thing to do -- it's the smart thing to do.

Congressman Markey’s comments on this week’s question are hardly surprising. He is, after all, co-author of the Waxman-Markey climate change bill that passed the House last year. Almost all objective analyses of his legislation concluded that it would do far more harm than good by imposing energy scarcity and other impractical mandates.

Markey’s characterization of skeptics and deniers, whoever they are, is a straw man to challenge the motives and integrity of anyone who raises serious questions about climate orthodoxy. For example, where is the increase in atmospheric water vapor that is needed for positive climate feedback or how can he be sure that the Pacific Decadal Oscillation is not a major driver in cloud formation which might explain most warming and cooling over the past century?

Demonizing and polarizing is hardly a way to move lawmakers to common ground on mitigating the risks of climate change or, for that matter, any other contentious issue. Wouldn’t the public be better served by identifying some steps that would enjoy broad support rather than giving into the inertia triggered by polarizing actions?

Most rational people do not question that human activities affect our climate system. The debate stems from uncertainty over our ability to reliably estimate that affect and to determine a cost-effective risk management strategy.

For the sake of argument, let’s accept that the effect of fossil energy use will be a world more than 1º warmer later this century—the best estimate absent positive feedback—but less than the 8º or so claimed by the climate lobby. The question then becomes what can we do to moderate the effects of such a temperature increase?

Global emission projections with or without Waxman-Markey are hardly distinguishable because US laws only impact US emissions and the developing world has become the major source of CO2 emissions. Developing countries are increasing their emissions in pursuit of economic development and higher standards of living. Do we really believe that we have the right to deny them those aspirations? Are we prepared to condemn almost 2 billion people to continued levels of poverty that are far worse than even the poorest communities in the Western world?

If we are going to slow the growth in emissions and, perhaps, eventually stabilize them, we are going to need energy systems far different from what we have today or are likely to have in the next decade. Those revolutionary energy systems not only have to provide enormous quantities of energy but have to do so at affordable prices and without large government subsidies. Achieving that future will require a R&D program perhaps on the magnitude of the Manhattan Project but sustained for decades. How will it be funded?

In the meantime, we need to:

• Explore all economically practical way to encourage the turnover of our large capital stock;
• Create incentives for more rapid deployment of new technologies;
• Promote greater deployment of energy technologies in the developing world; and
• Pay more attention to adaptation actions as a prudent form of insurance.

Last but certainly not least, we need to be realistic about what can be actually accomplished over the next few decades. Aspirations are fine. But if they are unrealistic, they breed the consequences of failure.

The headlines from the hottest year-to-date on record paint a dangerous climate picture, consistent with the overwhelming scientific evidence.

Based on the National Journal’s question, I think it’s important to distinguish between scientific skepticism and flat-out denial in the face of the facts.

Scientists, skeptical by both nature and training, always urge a dose of caution when looking at any one event as evidence of climate change. They look at the totality of events and discover patterns that help determine how our climate is changing.

Deniers, on the other hand, are eager opportunists, who will use single points of data, or single events (remember Snowmaggedon?) to claim that the patterns do not exist. Theirs is a world of scientific dishonesty and misinformation.

And it is the high level of professional skepticism--not the useless back-and-forth encouraged by deniers—that makes the overwhelming scientific consensus that climate change is real and caused by man all the more powerful. 97 to 98 percent of climate researchers support the fundamental conclusion of the Intergovernmental Panel on Climate Change (IPCC). The head of the National Academy of Sciences has indicated that we know more about the link between man and climate change than we do smoking and lung cancer.

Scientists have warned us that climate change will result in more frequent and intense heat waves and wildfires, increased drought and flooding, and accelerated melting of glaciers and polar ice. With that prognosis in mind, let’s review some of what has happened in 2010, which has seen the hottest January to July period on record.

RUSSIA:

Russia suffered both the worst heat wave and one of the worst droughts since record-keeping began more than 130 years ago. Some 25 million acres of land have suffered from drought damage, leading Prime Minister Putin to ban all exports of grain. Nearly another half million acres have been scorched by more than 800 wildfires and the death rate in Moscow doubled to 700 people per day as heat and smog descended on its streets. In India, temperatures in May reached 120 degrees, killing dozens and damaging crops.

PAKISTAN/CHINA/INDIA:

The extreme floods slamming much of Asia may prove to be one of the biggest humanitarian disaster in memory. In Pakistan alone, 1600 lives have been lost and 20 million people have been affected by flooding, threatening to further destabilize regions that are critical to our national security. Torrential rains and flooding in China have claimed at least 1800 lives this year.

GREENLAND:

In Greenland, an iceberg covering 100 square miles – more than four times the size of Manhattan – broke off the coast of Greenland. It is the largest piece of Arctic ice to break free in nearly half a century. The good news: This new iceberg provides plenty of room for global warming deniers to start their own country. The bad news: Leading scientist warned Congress this month that we may have already crossed a ‘tipping point’ in the Arctic.

HERE AT HOME:

And here in America, the only person not running from the heat has been LeBron James. Up and down the eastern seaboard, we have endured day-after-day of record-breaking temperatures. Mega-storms have rocked many regions of the country, including my home state of Massachusetts, where in March we had two “50-year” storms in two weeks.

Flash floods have shocked communities in Iowa, Oklahoma, and Arkansas. The damage inflicted on Nashville was one of the most under-reported stories of the year. More than 20 people lost their lives in Tennessee and property damage exceeded a billion dollars due to the flood that submerged Music City.

Take a step back from these individual pieces and we see a mosaic that could not be clearer. Our world is experiencing extreme events that are consistent with the warnings and observations of scientists. In the United States, record highs now occur twice as often as record lows and the amount of precipitation falling in heavy downpours has increased 20 percent nationwide over the last 50 years. As carbon pollution increases, so does the risk of extreme events.

DENYING CLIMATE SOLUTIONS COSTS JOBS:

As several publications have pointed out in editorials, 2010 should be a climate wake up call. Following the warmest decade on record, it begs the question: when will the Republican deniers in the U.S. Senate finally get to work on clean energy and climate solutions?

Hiding behind the circus of stolen emails from climate scientist is no longer an option. Multiple reviews in the UK and here at home have exonerated climate scientists and reaffirmed that the science of human-caused climate change is robust.

The delay and denial in the Senate is costing the U.S. economy millions of jobs and billions in private investment.

This month Deutsche Bank, which oversees $700 billion in funds and devotes $6 to $7 billion to climate projects, announced their intentions to move billions of dollars in private sector energy investment projects from the United States to China and Western Europe. They placed the blame on Washington policy makers who have failed to act on energy and climate legislation that would provide a stable investment environment for clean energy jobs and technology to prosper. "You just throw your hands up and say ... we're going to take our money elsewhere," said Deutsche Bank’s Kevin Parker.

And why are the clean energy investments and jobs flowing to China? This summer the United States’ main economic rival announced both a reduction in carbon emissions and a plan to invest $738 billion in clean energy over the next decade.

Last year, the House came together, worked through our regional differences, and put together a plan for energy and climate legislation. The Waxman-Markey legislation will create millions of new jobs and provide the regulatory certainty for private capital to begin flowing to projects in the United States.

The American people need jobs now. Building wind turbines, solar panels, and high mileage vehicles will heat up our economy while helping to cool down our planet.

Dr. Brenda Ekwurzel authored this post. Dr. Ekwurzel is a climate scientist at the Union of Concerned Scientists.

An unusually large number of extreme weather events have occurred around the world this summer. In Pakistan, record floods have displaced millions of people and killed more than 1,500. In China, torrential rains have caused massive flooding and landslides that have killed more than 3,000. In Russia, the worst drought in decades has triggered wildfires; during its worst the daily death rate in Moscow doubled to some 700, and a third of the country’s wheat harvest was wiped out. Meanwhile, closer to home, a number of states have been pummeled by heavy rainstorms, and more than a dozen states have suffered withering heat waves.

These extreme weather events are consistent with trends scientists say are caused by global warming. The most recent report by the U.N. Intergovernmental Panel on Climate Change (IPCC), issued in 2007, projected more flooding in Pakistan and China this century and noted that precipitation already has increased in both summer and winter over northern Pakistan and western China. It also projected a greater likelihood of drought conditions in parts of Russia.

As for the United States, both the IPCC and the U.S. Global Change Research Program found the heaviest rainstorms and snowstorms are depositing more precipitation today than decades ago. The heaviest storms, for example, are now dumping on average 67 percent more precipitation in the Northeast and 31 percent more in the Midwest.

Why is this happening? It turns out a warming planet is more likely to generate more severe precipitation in regions that typically experience rain or snow and at the same time increase the chance for drought in between the periods of rain. Put another way, in a warming world the light rains are getting lighter and the heavy rains are getting heavier. A warmer atmosphere absorbs and retains more water evaporated from the soil and bodies of water, including lakes, rivers and oceans. When storm clouds gather, the atmosphere is often holding more water, which is favorable for heavier than normal storms.

Higher temperatures are one of the hallmarks of climate change. According to NASA and NOAA, 2010 is on track to be the hottest year on record. And the last decade -- from 2000 through 2009 -- was the hottest decade since worldwide record-keeping began more than 100 years ago.

The extreme weather events we have been witnessing this summer are due to a combination of three main factors: climate change, which increases average temperatures and alters rainfall patterns; natural cycles, such as El Niño and La Niña; and human alterations of the landscape, such as clear-cutting forests and draining wetlands. As scientists improve models on a regional scale, they will be able to better determine the relative contributions of these three variables.

Of the three factors, the only ones we can control are the way we alter the land and the amount of heat-trapping gases we emit. We can avoid the worst possible consequences of climate change by protecting forests and dramatically reducing fossil fuel emissions. If we wait to collect more data to confirm what we already know, extreme weather events likely will occur more often and become worse.

To address this question, I am posting what the director of our Climate Change Program at The Nature Conservancy, Jonathan Hoekstra, has written the following about climate and weather:

After two months of record-breaking heat and withering drought, Russia is finally getting some relief. But not before extreme weather stoked wildfires that blanketed Moscow in choking smog, contributed to thousands of heat-related deaths and drownings, and shriveled one-quarter of the country’s wheat harvest.

Torrential monsoonal floods are still ravaging Pakistan, forcing as many as 20 million people from their homes and provoking concerns about political instability in an already unstable region.

Right here in the U.S. this summer, we suffered heat waves and witnessed downpours – as much as 10 inches in just 12 hours – that flooded towns and took lives in Massachusetts, Tennessee, Arkansas, Iowa, and Oklahoma.

Coincidence? Probably not. Weird weather is giving us a preview of what climate change means for people. All around the world, we are seeing hotter hots, wetter wets, and drier dries. These extremes, in turn, are resulting in destructive wild fires, choking air pollution, ravaging floods, lost crops, lost homes, and lost lives.

Data released from the U.S.'s National Oceanic and Atmospheric Administration (NOAA) and the National Climatic Data Center shows that June 2010 was the warmest month of June globally since record-taking began in 1880. It was also the 304th month in a row that has been above the 20th Century average. There is no question that our world is warming.

We are just left to wonder when, where and how the consequences will be felt. Warmer air makes for wilder weather because it holds more moisture. As warmer air masses move across the landscape, they can pick up more water from the ocean, from lakes and from the soil, creating drier conditions for crops and evaporating water supplies. Eventually, what goes up must come down, as moisture-laden air unleashes deluges of precipitation – such as the torrential snows the East Coast experienced this past winter.

This is probably the point where I am supposed to remind you that any single weather event cannot be definitively linked to climate change. But that’s not the point. If climate is what we expect and weather is what we get, we need to start changing our expectations. Record high temperatures are being broken twice as often as record lows; you would expect them to be equal if climate were steady. According the U.S. Global Change Research Program, over the last 50 years, heavy rainfalls in the Northeastern U.S. have increased 67 percent, and snowpacks in the Western U.S. are melting up to three weeks earlier.

These sorts of climate changes are serious business. Heat waves hurt air quality and threaten people’s health. Droughts shrivel crops and dry up water supplies. Floods wash away communities. As the news of the last few weeks has made so vivid, extreme weather costs money and costs lives. Climate change increases the odds that we will experience more wild weather and then suffer the consequences.

With so much at risk, we need to act now to stabilize the climate and safeguard our communities.

• We need policies that immediately reduce greenhouse gas emissions and wean us off heat-trapping fossil fuels and onto clean, low-carbon energy sources.
  
• We need to invest in protecting the world’s remaining forests that absorb carbon dioxide from the atmosphere and provide clean water and other valuable benefits.
  
• We need to help make nature more resilient to change so that people can keep counting on it for food, water, jobs, and protection from storms and floods.

We may not be able to control the weather, but, by strengthening nature, we can help reduce the odds that it will get more extreme.

You don’t need to look to Russia, Pakistan or Greenland to find evidence of global warming driving severe weather. As National Wildlife Federation Climate Scientist Dr. Amanda Staudt just reported this month, global warming is fueling this summer's heat waves right here in America.

Climate changes because that is what it always does. The climate system is chaotic, and one season’s weather or even that of several years is not a sufficient basis for another round of Chicken Little like panic. However, it would be a triumph of hope over experience to expect that this summer’s extremes will not lead for renewed calls to implement radical policies to severely restrict human emissions of CO2. Almost anything America does will have a trivial affect on atmospheric concentrations, because the developing world is increasingly the major source of those emissions. And it is a fact that they will continue to grow.

Recent extreme heat waves do not prove the existence of serious climate change caused by humans any more than last winter’s snowstorms disproved it. While there is no serious dispute that human activities associated with using fossil fuel and land use changes are affecting climate, the evidence for drawing definitive conclusions must come from long-term trends rather than individual events.

During the on-going climate change debate that has been raging since 1988, the ‘green’ movement has labeled any seasonal departure from the “norm” as evidence that human fossil energy use is having or going to have a catastrophic impact on the climate system. But, when these individual events are measured against objective data, it has turned out that nothing extra ordinary was occurring. It proves the wisdom of John Adams observation that “facts are stubborn things and whatever may be our wishes ... they cannot alter the state of facts and evidence.”

For most of this decade, temperature has not increased in spite of continuing increases in CO2 concentrations in the atmosphere. Alarmists asserted that this period of stability was too short to draw any conclusions. And yet, they now use this year’s weather to claim that it confirms their predictions of an impending apocalypse.

Over the course of climate history covering several million years, there have been extended warm and cold cycles. And for much of that period, the temperature was much warmer than it is now. Climatologist Roy Spencer of the University of Alabama has documented cycles that coincide with changes in temperature over the past century. His research has shown how the Pacific Decadal Oscillation “causes cloud cover that might be sufficient to explain most of the major variations in global average temperature since 1900, including 75 percent of the warming trend.” Other researchers have demonstrated using empirical data that hurricane activity and recent periods of drought are not unusual when compared with data covering the past 100 years.

The debate over the extent of human influence on the climate system will be settled when science can determine the climate’s sensitivity and whether the atmospheric feedback from fossil energy emissions is positive or negative. The research from climatologists like Roy Spencer and Dick Lindzen suggests that it is negative.

Scientists and carefully-treading advocates are often quick to note that no single weather event is irrefutable proof of (or against) global warming. Weather is the day to day variability in temperature and precipitation that always gives us something new to talk about, while climate is the long term average pattern of trends, which we probably should talk more about.

What scientists can say, and what is probably more relevant from a policy perspective, is that global warming is likely to increase the incidence of weather extremes. In other words, by loading the atmosphere with emissions from fossil fuel-burning, we are weighting the climate dice in favor of wild and weird weather.

Warmer air can hold more moisture, which can in turn lead to heavy precipitation. On a warmer planet, for instance, what was once considered a 100-year flood event may come many more times in a century. For some areas, though, droughts are likely to become more severe. Warmer ocean waters can supply more energy for stronger hurricanes. And daytime and nighttime high temperatures are likely to be broken.

Many people are comparing this year’s crop-withering heat wave in Russia to the heat wave that took more than 52,000 lives across Europe in the summer of 2003. Scientists looking back at the European heat wave estimate that human-induced global warming at least doubled the odds of that event occurring. Looking forward, climate models show that Southern Europe could experience such conditions as frequently as every other year if fossil fuel emissions are not cut dramatically.

This year, the extreme heat and drought and wildfires in Russia have hit food production hard, causing the country to ban grain exports for the rest of the year and pushing up global wheat prices. But the next dangerous heat wave could well hit an even larger player on the world food stage, like the U.S. Midwest, which supplies well over half of the internationally-traded corn. Or it could happen in China, with over 1 billion mouths to feed. Global warming is increasing the odds of this happening, but unfortunately for us, agriculture evolved under a remarkably stable climate, not one so prone to high temperatures and extremes.

The tendency towards more extremes and less predictability is a large part of the reason why some of the most powerful voices warning about global warming come from those tasked with managing risk: insurance companies, intelligence agencies, and the armed services. Policy makers on whom we rely to protect national security would also do well to pay heed.

Dr. Jay Gulledge authored this post. Dr. Gulledge is senior scientist and director of the science and impacts program at the Pew Center on Global Climate Change.

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.”

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.

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, from a national security perspective, are of great interest to the United States: 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. The UN calls this crisis the world’s worst humanitarian disaster in recent history. Meanwhile, Russia is locked in the worst heat wave and drought in its documented history. The combination of extreme heat and thick smoke and smog from wildfires near Moscow doubled the city’s death rate at the peak of the heat wave earlier this month.

Secretary of State Hillary Clinton and UN Secretary General Ban Ki-moon are among the high-ranking officials who have made recent statements linking extreme weather events like the floods in Pakistan to climate change.

So we face the key question: What can be said 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. 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 observed 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 occurred 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 large, stationary patterns of high atmospheric pressure known as “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. Furthermore, there is no scientific basis for arguing that these events have nothing to do with global warming, because the global warming effect cannot be completely isolated from natural events. In other words, any given event may have happened even without climate change, but climate change may have made it more severe and increased the probability that such an extreme event would occur.

Increased attention to extreme weather events underscores the urgent need for meaningful domestic and global action on climate change. The U.S. has a leadership role to play globally that largely hinges on its ability to take effective steps to reduce carbon pollution at home.

(These comments are from Andreas Muenchow, physical ocean science and engineering professor at the University of Delaware. He recently testified in front of the House Global Warming Committee on this issue.)

No, climate does not cause weather, the balances of forces, masses, and energies in the atmosphere do. Furthermore, the atmosphere interacts with oceans, ice sheets, lands, and livings things. Ask an equally ill-posed question “Is climate change contributing to wild weather?” and my answer becomes yes, but with the caveat that butterflies flapping their wings in Tokyo contribute as well. There is more to the question than meets the eye.

Globally averaged air temperatures have increased by about 0.6 degrees Celsius per decade over the last 50 years. This warming is not uniform as it varies in both space and time. Some places cool, some places warm, some places cool or warm more than expected. Floods, droughts, mudslides, and calving glaciers always have and always will occur. Some weather events separated in space and time are physically linked via large-scale tele-connections such as Rossby waves in the atmospheric jet stream or the El Nino-Southern Oscillations.

So, how much of the currently observed extreme weather events are due to globally increasing air temperatures that also coincide with globally increasing ocean temperatures? Does global warming increase, say, the intensity of hurricane by 1% or 10% or 50%? These much tougher questions are at the forefront of both observational and computational work on environmental physics. The IPCC numerical models and new understanding of key physical processes, I feel, are the only way to attribute global warming effects on extreme weather events. Ice-ocean interactions around Greenland are one such physical process poorly incorporated in IPCC models. Another such process is the way that hurricanes may dominate the ocean heat flux towards Greenland.

Three weeks before Katrina hit New Orleans in 2005 MIT professor Dr. Kerry Emanuel published that the power dissipation by hurricanes has increased by about 60% over the last 30 years and that this increase correlates with increasing sea surface temperatures in the tropical North Atlantic. Nevertheless, Dr. Emanuel himself stressed that nothing could be more absurd than stating that Katrina was caused by global warming. Furthermore, refining his methodology in 2008, he finds that “… global warming should reduce the global frequency of hurricanes, though their intensity may increase in some locations.” [Emanuel et al., 2008: Hurricanes and global warming, Bull. Amer. Meteor. Soc. 89, 347-367.]

Just because a pattern of extreme weather events feels like evidence of global warming, it does not make it so. This scientific uncertainty, however, should not distract from the potential costs that a potentially man-made climate change will cause. Climate zones may shift, sea level may rise, volatile weather events may become more volatile, etc. All of this may cause additional political instabilities in marginally stable nation states ill-equipped to deal with either natural or man-made disasters.