Scientists from around the globe, working with a variety of models and data sources, have identified a substantial risk that, unless we act quickly, human-induced climate change will lead to an increase in extreme weather.

Whether the most recent droughts, tornadoes and floods are a direct result of climate change is certainly an issue worthy of further scientific study. But we needn’t wait for the answers to begin moving forward on reducing our greenhouse gas output—the risks of a warming planet are already significant enough to warrant action now.

One thing is for sure, extreme weather of the kind we’ve seen recently is expensive. Even if we can’t yet be sure of the causes of the wildfires in the southwest or the intense snow melt in the north, these events give a glimpse of the potential cost of climate change. Time recently reported the amount of damage due to extreme weather to be around $485 billion dollars a year in the United States (or 3.4% of the national GDP).

And with scientists suggesting that extreme weather could get worse and more frequent as the thermostat rises, those costs could mount. The effects could include more downpours in already wet areas, longer dry spells in arid areas, and earlier snowmelts.

The risk of these kinds of weather patterns becoming the new normal is what climate scientists and economists want to avoid. A poll of top economic experts reinforced found a clear consensus that climate change has the potential to impose substantial costs on the U.S. and global economies.

It’s because of this huge potential price tag, a strong majority of these economists support taking steps now to slow down emissions. Even in the face of uncertainty, attempts to lessen the damage carry tremendous value.

Just as many people are unlikely to get into a massive car accident, automobile insurance is still a smart buy. In the same way, preventatives measures against climate change are worth some costs—they’re our insurance against the catastrophic events of global warming.

Certainly, more research is needed to study the connections between these recent disasters and climate change to help us better understand the risks we are imposing with greenhouse gas emissions and plan for the future. But there is no reason to wait to cut down on those risks now. If anything, the recent spate of natural disasters and extreme weather is a stark reminder of what we stand to lose if we allow greenhouse gas emissions to go unchecked.

Climate scientists have long been cautious about attributing individual extreme events (hurricanes, floods, droughts, etc.) to the effects of climate change. That might be in part because skeptics delight in pointing to large snowstorms as evidence against climate change (see Senator Inhofe’s igloo), ignoring the fact that even these seemingly paradoxical types of events are actually completely in line with the predictions about a climate system that contains more water and more energy. However, as Scientific American put it in their excellent three-part series last week, “The signal of climate change is finally emerging from the noise” of the inherent variability of the climate system. And as the number of extreme weather events build, it becomes ever more critical to study these connections. The answers have real implications for our own well-being and for the future of our wildlife and the habitats on which they depend.

Does our conception of what constitutes a 100-year flood need to change? The answer matters, both for communities whose flood risk may be much higher than they thought, and for bottomland and riparian habitats that nourish everything from fisheries to waterfowl. Are massive droughts on the increase? The answer certainly matters to our agriculture producers, it matters to people who live in fire-prone areas, and it matters to wildlife habitats as well. And the effect of climate change on the strength of hurricanes matters to all of our coastal residents, human and wildlife alike.

Meanwhile, some in Congress are not content to simply avoid addressing the root causes of climate change pollution, but are additionally now trying to prevent the government from even preparing for and responding to the impacts of climate change. Last month, the House of Representatives voted to strip funding for climate change preparation from the Department of Homeland Security -- that’s the department that includes FEMA, our main federal responders to climate-related disasters, and from the Department of Agriculture—as if extremes of flood, drought and temperature couldn’t possibly have any effect on the food supply. This game of politics has to stop. It’s time members of Congress act like grownups and make responsible decisions for the future of this country. Our wellbeing, even our lives and the health of our planet depend upon it.

More Carbon Dioxide Emissions = More Warming = More Extreme Weather

The science is clear: Warmer temperatures accommodate more water vapor in the atmosphere. This in turn leads to more instability and increased risk of extreme storms and weather events. And we are indeed seeing more extreme precipitation events than a century ago, in line with the 1°F temperature increase over this time. Scientists have also measured increases in atmospheric water vapor and the height of the lower atmosphere (the tropopause) over the past three decades, consequences of a warmer atmosphere.

Of course, because climate is the accumulation of weather over a period of many years, any single storm, flood or wildfire cannot be singularly attributed to global warming. However, it seems very possible that we are now experiencing an altered climate regime that will only be definitively linked to human-caused climate change over the coming decades – through the rearview mirror of accumulated climate science.

The problem with waiting to act until all the nuances of the relationship between warming temperatures and extreme weather can be further established is that we may lose our chance to avoid what could be truly catastrophic impacts of a climate out of control.

In the year 2010, and the first half of 2011, we have seen extraordinarily wild weather, perhaps the most extreme set of weather events on Earth in more than a century. Meteorologist Jeff Masters, Ph.D, co-founder of the website “The Weather Underground” suggests this confluence of weather may be more than chance: ”… [I]t is highly improbable that the remarkable extreme weather events of 2010 and 2011 could have all happened in such a short period of time without some powerful climate-altering force at work. The best science we have right now maintains that human-caused emissions of heat-trapping gases like CO2 are the most likely cause of such a climate-altering force.”

As the National Academy of Sciences has noted, the effect of growing carbon pollution from human activity is ramping up the risk of hotter summers and both more devastating droughts and heavy rain events, while significantly increasing the area burned by wildfires in the American West. It is also accelerating the melting of mountain glaciers and the Greenland ice sheet, contributing to rising seas.

NOAA’s peer-reviewed 2010 State of the Climate report observes that in 2010, Greenland glaciers lost more mass than in any year on record. Increasingly, scientists expect that sea levels will rise by as much as three to five feet in this century, threatening the Miami-Dade metro area and many other coastal areas.

And there is also good evidence that hurricanes can be expected to intensify as the climate warms.

But the climate system is complex, and further research is needed to tease out how recurrent climate patterns, such as El Niño/La Niña and the North Atlantic Oscillation, interact with globally warming temperatures. Further study about whether hotter temperatures and other changing climate patterns are related to the formation of tornadoes is also warranted to determine whether or not there is a link to this particular type of weather event.

This ongoing need for scientific research, by the way, is precisely why Congress should be encouraging, not blocking, the National Oceanic and Atmospheric Administration’s (NOAA) effort to open a Climate Service. NOAA’s proposal, under dispute in Congress, would create a structure capable of more efficiently providing authoritative, timely, and reliable information about climate variability and change to state and local governments, farmers and other businesses, and managers of transportation systems and water supplies. The scientific climate data collected by NOAA is already in demand. A national climate service will assist local business, government, and community leaders to plan for future anticipated changes in climate.

Faced with the growing evidence of the implications of climate change for our society, we can take two broad categories of action in response: First, we can reduce emissions. Many businesses and households have been doing this, because in many contexts, carbon pollution equates to wasted fuel and energy. Jurisdictions such as California are embarking on broad efforts to reduce emissions. And as recently reported, the Obama Administration is considering steps to reduce carbon pollution from vehicles while reducing oil consumption.

Preparing for the impacts of climate change is also essential. The New York Times reported recently on Chicago’s efforts to adapt to a future climate that will be more like that of Baton Rouge. And business leaders are assessing the risks posed by climate change, and preparing to adapt. For example, Entergy Corporation recently co-sponsored a report on quantifying and managing climate risks such as stronger hurricanes and higher seas – in the Gulf Coast.

A broader national policy that would take long-term steps to cut carbon pollution by putting a price on it is still needed. But while we are waiting for our national leaders to refocus their attention on this, many cities and business leaders are moving ahead to make prudent plans to reduce risk from climate impacts.

Scientists have known about the reality of climate change for decades. The science tells us that as the Earth warms, we will see more frequent heat waves, drought and heavy rains. Now, with extreme weather happening with increasing frequency around the world, we can see that reality on an almost daily basis.

Despite this, we still hear claims that the science isn’t settled on manmade climate change. But to say this is simply to ignore reality. The science is clear that humans are warming our climate, based on evidence that has been evaluated over and over again. It’s a reality that 2010 was tied for the warmest year on record. It’s a reality that 100-year floods and 1000-year floods are on the rise. And the reality is crops are failing as a result of historic droughts everywhere from Texas to the Horn of Africa.

Bad weather is nothing new — but manmade climate change is making extreme weather far more likely. We should absolutely encourage further research on the links between weather and climate, including the possibility that climate change is leading to more destructive tornadoes. What we know already is that climate change is no longer an abstract idea that we can put off until far in the future. It is happening now. As those with an interest in maintaining the status quo try to stir up debate, we are losing precious time we could be using to find solutions.

Evidence for the ill effects of climate change is all around us: already this year nearly 5 million acres of land in America have been ravaged by uncontrolled wildfires, and an estimated 2.5 million acres of productive farmland have been lost to flooding. This week alone, more than a million acres in this nation will burn, and people across Minnesota and North Dakota will be forced out of their homes as floodwaters rise to record levels. The year 2010 saw the highest number of nations ever to set record temperatures, and ice in Greenland melted at record rates. In just six months, 2011 has already been the most deadly and most expensive tornado season on record. Individually, no single extreme weather event is proof of a broader trend, but collectively this “new normal” of extremes is impossible to ignore.

At this point, 99% of scientists agree that human behaviors are causing climate change. One of the primary impacts of climate change is to increase the number and the severity of extreme weather events. Yet some in Washington and in think tanks funded by the oil and coal companies are still sowing doubt in Americans’ minds. The true costs of the inaction that results from this denial of the obvious will become more apparent with each passing year, and history will not be kind to those who held us back from responding to the climate crisis.

Yet the true tragedy will be felt – and is already being felt – on the personal level. As people see their life’s possessions burn or float away, the question we should be focusing on is not “are we sure that climate change is the cause of this particular disaster” but rather “have we done everything feasible to prevent this and other disasters from occurring?” As long as the bickering of climate science deniers continues to prevent action like comprehensive clean energy and climate legislation, the answer will be a resounding “no.”

While a small yet vocal minority choose to deny scientific reality, it is impossible to deny the economic and human toll of these widespread disasters. As the population grows and urbanized areas expand, the cost of each disaster grows. In 2009, natural disasters cost insurers about $110 billion; in 2010, the cost doubled to $218 billion. The interconnected global market relies on supplies and labor from around the world, so a single disruption can result in delays and costs to economies around the world. The “Groundhog’s Day Blizzard” left a path of snow and ice from New Mexico to New England that cost the US an estimated $1 billion in damages, while damage from the April 25 - 28 super tornado outbreak was estimated at $3.5 - $6 billion, making it the most expensive tornado outbreak of all-time. The Journal of Economic Perspectives has estimated that the total financial cost of Hurricane Katrina is $156 billion dollars. And none of these estimates includes the awful toll in human life. Whether we pay for climate change in advance or in the wake of ravaged towns, the price will be paid and costs are growing.

The costs of these climate-related events are already too much for our nation to bear, and they will only get worse the longer we fail to act. We should be looking at the increased incidence of floods, droughts, hurricanes, blizzards, and fires, and recognizing that we need to address climate change as an insurance policy against this damage. A smaller payment ahead of time – in the form of clean energy investment and pollution control – can prevent the worst effects of climate change and its devastating costs down the road. The costs faced by polluters under such a policy would pale in comparison to the costs of allowing greater environmental disasters to destroy towns and take lives. Even those who choose to deny the experts on the danger of climate change, should acknowledge that reducing our energy waste will improve our energy security, our air quality and public health, and will reduce the billions of dollars that we export to other countries for our energy.

Starting two decades ago, I spent many years performing statistical analyses of global temperatures in an attempt to identify both long-term trends and recurring cycles and their causes. One of the causes I identified was lunar cycles, which can impact sea surface temperatures by mixing colder deeper water with warmer surface water. I was (and still am) convinced that I’d found a fairly small, but significant, contributor to climate cycles, and I managed to convince most of my doctoral committee of the same. Unfortunately, my advisor remained largely skeptical. For me, it was a powerful lesson in the difficulties associated with the oft-repeated adage: correlation does not prove causation.

Despite powerful reasons to believe that a more energetic (warmer) climate will result in more energetic (extreme) weather, even when both actually occur it’s still difficult to prove that one caused the other. Although I haven’t been a practicing climate scientist for many years, my guess is we won’t establish clear proof between a warmer climate and more storms until years after we’ve seen an indisputable increase in the number of storms—and even then people will spend a long time arguing about it. Scientists may be able to predict it will happen, and we may see it happening, but that still doesn’t prove causation.

This leads to a challenging question more related to my current job: How do businesses look at the risks associated with climate change?

For some businesses, such as the reinsurance industry, extreme weather events are the greatest threat. These industries can’t wait until a causal link is proved before figuring out how their businesses will survive the change.

For other industries, the greater concern is not the direct impact of climate change, but the regulatory risk. If Congress were to act now to gradually and predictably phase in a program employing market forces to reduce emissions in the most efficient way possible, the regulatory risk for most industries would be fairly small. If Congress ignores the problem (as it’s doing now) and leaves the Courts and the Agencies fight it out, businesses will be left with substantial legal and regulatory risks. If future events, such as a run of especially extreme weather, galvanizes the public and leads to Congressional action and a sudden swing in national policy, the regulatory risk increases even more.

These are the type of questions businesses face on a daily basis. Businesses have to make their own assessment of the science of climate change and the direct impacts it may cause, whether the issue overall is likely to fade away or become more important, and the possibility of legal, regulatory, or political ramifications. In the absence of clear action from Washington, the importance of these risks has grown both to business and IETA. IETA’s next Symposium, to be held October 17^th in Washington, DC will focus on how businesses assess the risks—direct, regulatory, or otherwise—of climate change.

While no particular storm or weather event can be blamed on global warming, scientists around the world have continually warned that unmitigated climate change would lead to more extreme weather events, including more severe heat waves, more intense droughts and stronger deluges. Yet we still have not done enough to put in place comprehensive clean energy solutions that reduce dangerous carbon pollution and combat the worst impacts of global warming.

Sure, there are a number of factors which contributed to making April one of the most destructive months of tornadoes on record. However, studies have shown that global warming may create atmospheric conditions that are more favorable for producing tornadoes, since a warmer ocean and atmosphere will provide more water vapor that fuel severe storms. This year has also seen record flooding in the Mississippi and Missouri rivers and wildfires raging across Arizona and throughout the West.

And as if the tornadoes, flooding and wildfires seen in 2011 haven’t been scary enough, experts are warning that we have even more to worry about this year. Record-high temperatures are expected and an above normal hurricane season in the Atlantic Ocean is being forecast by NOAA.

Yet what we’ve always known about natural disasters is that while we can’t control the “natural” part, we have got to deal with the “disaster”. That includes taking responsibility for the causes we can, including our overuse of fossil fuels which is the leading driver of man-made climate change. And if it can help stem the magnitude and frequency of disasters like the one experienced by Joplin, Missouri, then why wouldn’t we tackle the one factor that experts agree humans play a role in? Now is the time to act.

Especially since, according to Newsweek’s Sharon Begley, our nation is just not prepared to deal with the intensifying and more frequent extreme weather events we are experiencing. She writes “Across the U.S., it’s just beginning to dawn on civic leaders that they’ll need to help their communities brave coming dangers brought by climate change, from disappearing islands in Chesapeake Bay to dust bowls in the Plains and horrific hurricanes in the Gulf of Mexico. Yet only 14 states are even planning, let alone implementing, climate-change adaptation plans, says Terri Cruce, a climate consultant in California.”

There is nothing to lose and everything to gain. While communities in the U.S. should be doing everything they can to adapt to the impacts of climate change on their regions, the solution our nation really needs to curb the severity of these impacts is to transition towards a clean energy economy that creates jobs, reduces our unstable dependence on oil, and can help reduce the risks of these extreme and deadly weather events.

The IPCC [Intergovernmental Panel on Climate Change] defines “climate change” as a change in the statistics of weather occurring over 30 years or longer and persisting for decades. Thus, the detection of a change in climate requires long-term records. To suggest that particular extreme weather events are evidence of climate change is not simply wrong, but the wrong way to even approach the issue — every bit as much as the claims made during a particularly cold and snowy winter (or even several in a row) that such events somehow disprove climate change. Weather is not climate and short-term climate variability is not climate change.

The detection of changes in climate requires looking at actual data.

The data on events that have captured our attention this year -- tornadoes, large-scale river floods (in unaltered river basins), and landfalling hurricanes -- shows no evidence of trends in the direction of more extreme events. This should not be surprising, because even if we assume a strong signal in extreme events from human-caused climate change, the statistics suggest that it would take many decades, and probably longer, before such signals would be detected.

Given this context, claims that particular events can be attributed in a causal fashion to human emissions of greenhouse gases are simply unscientific if not fundamentally incoherent. It is true that overall damage from tornadoes, floods, and hurricanes has been increasing in recent decades. A recent literature review of extreme event impacts around the world found that everywhere that researchers have looked, this increase can be entirely explained by increasing value of property at risk and increasing exposures to these hazards.

Human-caused climate change is real and deserves effective policies in response. The making of claims that are scientifically unsupportable will not further that effort. When they assert a linkage between recent disasters and human-caused climate change, advocates for action actually empower their opponents by giving them an easy-to-hit target.

This is all the more ironic because the arguments for better adaptive responses and improving our energy policies in ways that reduce reliance on fossil fuels make good sense regardless.

(These comments were submitted by Dan Lashof, Director of the Natural Resources Defense Council Climate Center).

The amount of heat-trapping carbon dioxide in our atmosphere has increased by one-third primarily due to burning coal, oil, and natural gas. Our climate is changing as a result, and as our climate changes floods, droughts, and wildfires are becoming more severe.

We are not just loading the dice, we are upping the ante, or as Steve Sherwood puts it in an excellent three-part series published by Scientific American, "it is more like painting an extra spot on each face of one of the dice, so that it goes from 2 to 7 instead of 1 to 6. This increases the odds of rolling 11 or 12, but also makes it possible to roll 13." In the same series, Deke Arndt of NOAA explains the link between climate and extreme weather this way: "Weather throws the punches, but climate trains the boxer."

Extreme weather turns climate change from an abstract concept about remote events, such as melting ice and drowning polar bears, to a concrete, often calamitous, experience for many Americans…if they connect the dots. Unfortunately, despite the vast amount of air time and pixels devoted to covering floods, storms, and wildfires in recent months, there has been very little discussion of the increasingly clear links to climate change. No wonder only about half of Americans understand that global warming is making floods, droughts, and wildfires worse, according to the latest Six America’s survey.

Scientists will continue to debate the details, and ideological deniers will continue to debate the facts, but more and more communities across America are getting on with preparing to deal with the reality of climate change. As John Holdren, the president’s science advisor, has said, it’s time to confront climate change by “managing the unavoidable and avoiding the unmanageable.”

"All of a sudden we're not talking about polar bears or the Maldives any more. … We're talking about homes and schools and churches and all the places that got hit."

– Nashville, Tenn., resident and writer Amanda Little, quoted in Scientific American about the 2010 flood.

Global warming increases the risk of extreme weather. Just as a high-cholesterol diet is a well-known risk factor for heart disease, science has demonstrated that global warming is a risk factor for extreme weather.

We are all familiar with weighing risks in our daily lives. For instance, do I drive to work and risk a traffic jam or take the subway and risk a cramped commute?

Thinking of global warming as a "risk factor" is a good way for people to wrap their heads around the link between climate change and extreme weather. For instance, a doctor cannot predict when an at-risk patient will have a heart attack, but she can confidently warn the patient that he is more likely to have an attack if he continues smoking and eating too much of the wrong types of food.

When it comes to the risks of climate change, key questions involve the science, costs, and responses.

Climate statistics show there are long-term trends of increasing heat waves and heavy downpours in the United States, and climate models simulate these trends when CO2 concentrations are elevated. We understand the physics behind these trends, and they are expected to continue as the world warms. That’s strong science, and it gives us confidence that the risk of extreme weather is rising because of human-induced global warming. Moreover, data from the world’s largest re-insurance company indicates that the number of weather and climate related disasters worldwide more than doubled over the past 30 years.

Like the rising costs of health care, the rising costs of weather impacts are deeply cutting into our economy. Recent analysis by Jeffrey Lazo at the National Center for Atmospheric Research finds the economic value attributable to weather variability could be as high as 3.4 percent of GDP, or $485 billion annually.

Some of these costs get passed on to the American taxpayer. Flooding is the single biggest economic impact of extreme weather, and the National Flood Insurance Program is the government’s second largest fiscal liability after Social Security. The program is already $16 billion in debt, and premiums currently do not reflect the risk of extreme weather. This massive liability is growing due to the increase in extreme weather risk from both socio-economic trends – more people live on the coast, for example – and the inexorable trend of increasing greenhouse gas concentrations.

Simply put, the increasing number of extreme weather events is a wake-up call of the costs we will incur over time if we fail to address climate change. Story after story describes communities across our country being hit by extreme weather events – the floods along the Mississippi, Missouri and Souris rivers, record-breaking drought in Texas, and wildfires in Arizona, Florida, New Mexico, and Texas. We see vivid photos of temporary levees being built around nuclear power plants and wildfires threatening stored plutonium in New Mexico. The stakes are high for the economy and for safety and security.

In the face of more and more extreme weather events, the American public wants to know: What’s going to be done about it?

Climatologists have likened the rising risk of extreme weather to gambling with loaded dice where an extra dot has been added to each face. Not only are we likely to roll 11 and 12 more often, it's also possible to roll 13! – such as North Dakota’s Souris River breaking a 130-year-old flood stage record by almost four feet, or the driest nine-month period in Texas history. When you know you’re playing with loaded dice, your best bet is to get out of the game.

The wonderful thing about risk is that it was invented to be managed. In the case of climate change, managing the risk means reducing greenhouse gas emissions to reduce the rate and ultimate amount of change, and increasing our resilience to changes that are already underway. We know this will impose costs. But make no mistake, inaction carries a price tag too, and that cost has too often been ignored in debates about how society should respond to climate change.

Recovering from the impacts of extreme weather events is likely to be far costlier and more disruptive than acting to reduce the risks. Doesn’t it make more sense to put in place a balanced program that will both reduce greenhouse gas emissions and make the necessary investments to make our communities more resilient to extreme weather events?

There are some facets of the climate debate that really aren't in doubt.

Carbon dioxide and other greenhouse gasses cause the earth's atmosphere to retain more of the heat that comes in from the sun, and radiate less of it back out to space.
Heat is the engine which drives the weather. Heat increases the amount of water vapor in the atmosphere, and increases the amount of free energy which drives the winds.
So more heat equals more violent weather.

It's no different than a pot on a stove. If you keep the flame constant, and put a lid on the pot, the spaghetti sauce gets hotter, If it's close to boiling, the currents within it become more violent, and eventually, if you seal the lid adequately it boils over.

But as every cook knows, guessing exactly how tightly you can fit the lid before the pot boils over is no mean feat. And if you get it wrong, and seal too tightly, by the time you notice your spaghetti sauce is boiling over, it's probably too late to solve the problem.

Even with the greenhouse gas concentrations of the pre-industrial era, much of the world suffered from extreme weather -- so the pot was already close to boiling over when we first started burning coal. We know that we have increased the concentration of CO1 in the atmosphere -- indeed that we have doubled it. We know that the mean global temperature is getting warmer. We know that extreme weather events are increasing in frequency. We know that more CO2 is likely to mean higher mean temperatures and that higher mean temperatures mean a more violent weather system with more extreme events.

The spaghetti sauce is already beginning to spatter, and spatter more violently.

Now you can argue that any particular spatter might have happened anyway, even if you hadn't put a lid on the pot. Who cares? What's important is how violent and frequent the spatters are. And if someone came into your kitchen, watched the spaghetti sauce start boiling over and said, "Don't take the lid off the pot, It might have happened anyway," no cook would listen.The fact that we always had and would have had some floods, fires, famines, hurricanes and tornadoes does not make it a good idea to increase their frequency.

Nor is the argument that perhaps some of the current warming is due to some external cause -- say sunspots -- reassuring. If you were facing a completely natural heat wave in your house and were about the pass out from heat exhaustion, you would not turn up the furnace! You would turn on the air conditioning. Even if some of the mean increase in global temperature is not caused by increased, man-released greenhouse pollution, that is not an argument for continuing to make the problem worse.

Look at recent events:

2010 tied with 2005 for the warmest year on record.
Every month since 1985 has been warming than the average for the 20th century for that month. We have not experienced, globally, a single cold month in 25 years.
So much ice has melted at the poles that the earth has gotten measurably thicker around the equator. The Greenland Ice sheet melted more last year than in any year in the previous decade. Melting of high altitude glaciers has also caused the earth's rotation to change measurably. The Andes are higher than they were because their glaciers no longer press them as hard.
Extremes of low and high salinity in the oceans, driven by extreme precipitation, reached record levels.
We had a record year for and losses from tornadoes in the US.
We had not one but two major, "100 year+" flood events in the Mississippi River system.
Australia had the wettest spring in record -- following the worst drought. (It's the extremes that kill you, the loss of a pattern.)

I could go on. But instead, let's start taking the lid off the pot, and letting the excess solar energy that our greenhouse pollution has been keeping in escape before we have a serious boil over.

(These comments were submitted by Nathan Willcox, Federal Global Warming Program Director, Environment America.)

Global warming increases the risk of extreme weather, from floods and more intense hurricanes, to droughts and more devastating heat waves. Numerous scientific studies have said as much, and I co-authored a report last fall that examined the most recent studies making this connection—and also documented the damage that has been caused by recent extreme weather events across the U.S. Given this link, the damage caused by the extreme weather we’re already suffering through today drives home the need for the U.S. to get far more serious about cutting global warming pollution than has been the case thus far.

Our report looked at several links between global warming and extreme weather, but a few findings stood out. Unchecked global warming could double the number of intense Category 4 and 5 hurricanes in the Atlantic over the course of the next century. The Gulf communities still recovering from the devastation of Hurricane Katrina offer a glimpse of why this warning cannot be ignored. That hurricane alone is estimated to have caused $134 billion in damages.

Heat waves—among the most lethal of extreme weather events—are projected to be more frequent, more intense and last longer in a warming world. By the end of the century, parts of the nation, particularly in the West, may experience a once-in-20-years heat event (based on the historical record) as frequently as once every other year, while the number of 90 degree days will more than double in the southern part of the country. A 2006 heat wave that affected the entire contiguous United States was blamed for at least 147 deaths in California and another 140 deaths in New York City, while thousands died in Russia during the heat wave that country suffered through last year.

Extreme precipitation events and flooding are also expected to become more frequent due to global warming. Already, a separate Environment America report found that the number of heavy precipitation events in the U.S. increased by 24 percent between 1948 and 2006. And even after the water recedes, the damage from floods can be devastating. The Midwest floods of 2008—the region’s second “500-year” flooding event in 15 years—led to 85 of Iowa’s 99 counties being declared disaster areas. 40,000 Iowans were forced from their homes and total job losses stemming from the flood were estimated at 7,500. The American Farm Bureau estimated that there were $4 billion in agricultural losses in Iowa, contributing to total damages estimated by state officials at between $8 billion and $10 billion.

In short, extreme weather causes extremely big problems. And while scientists don’t know exactly how many more deadly heat waves we’ll see or exactly how many more downpours we’ll suffer through with every uptick in the mercury, we’d be foolish not to do everything we can now to avoid an increase in the frequency and intensity of extreme weather events in the future. And that means cutting global warming pollution.

In the near term, it means President Obama should ensure that the cars and light trucks of tomorrow are much cleaner and more fuel-efficient than the cars of today, by setting standards requiring the average new car to meet a 60 miles-per-gallon standard by 2025. It means Congress should spend less time trying to block the Environmental Protection Agency from pursuing commonsense measures to cut global warming pollution, and more time passing policies to advance energy efficiency and renewable energy solutions. And it means the states must continue to lead the way in the absence of more proactive federal-level efforts, most notably through state and regional pollution-reduction plans like the Regional Greenhouse Gas Initiative (RGGI).

As with many other aspects of global warming, our elected officials have a choice: they can continue to listen to the talking heads on the right and the ExxonMobil’s of the world who say we should ignore the warning signs and question what 97 percent of climate scientists are telling us (that climate change is occurring and that human activities are the primary cause), or they can heed the scientists’ warnings and start putting to work the global warming solutions we’ve had at our fingertips for years. For the sake of future generations and this one, I hope they choose wisely.

Before getting to the substance of this question, it is important to correct what is a miss- or over-statement. “Skeptics”—at least the vast majority—do not deny the occurrence of global warming. Instead, they question the degree to which such temperature changes over the past century are due to human activities and, consequently, how effective costly, government mandates to restrict our behavior would be at combating the phenomenon.

Science hinges on what we don’t know rather than what we do. That’s why the scientific method uses observation, empirical data, and testable hypotheses. Too much of what passes for science in the climate debate is little more that advocacy wrapped in the trappings of science—leaving us rich in opinion and poor in good data. In his national bestseller A Short History of Nearly Everything<http://www.scribd.com/doc/48612324/the-short-history-of-nearly-everything-bill-bryson>, prominent liberal author and self-described cheerleader for science Bill Bryon notes:

How can scientists so often seem to know nearly everything but then still can’t tell us whether we should take an umbrella with us to the races next Wednesday?

In his chapter on climate, Bryson explains (emphasis added):

It is mildly unnerving to reflect that the whole of meaningful human history - the development of farming, the creation of towns, the rise of mathematics and writing and science and all the rest - has taken place within an atypical patch of fair-weather. Previous inter-glacials have lasted as little as eight thousand years. Our own has already passed its ten thousandth anniversary …

For most of its history until fairly recent times the general pattern for Earth was to be hot with no permanent ice anywhere. The current ice age - ice epoch really - started about forty million years ago, and has ranged from murderously bad to not bad at all. Ice ages tend to wipe out evidence of earlier ice ages, so the further back you go the more sketchy the picture grows, but it appears that we have had at least seventeen severe glacial episodes in the last 2.5 million years or so - the period that coincides with the rise of Homo erectus in Africa followed by modern humans.

In light of this background, assertions by global warming advocates that any extreme weather event is triggered by human-caused global warming appear dangerously out of touch. For these true believers, wet or dry, freeze or fry the cause is always the same and so is the solution—elimination of fossil energy consumption.

In the case of the hurricanes, claims that elevated water temperatures in the Gulf of Mexico caused hurricanes to be more extreme were discredited when data showed that the temperature levels in the Gulf in 2005 were not out of line from those of previous decades. Activists conveniently ignored the fact that there’s a 30-year hurricane cycle. The low point in the previous cycle occurred around 1995, so the past decade fell within the increasing phase of the cycle.

That brings us to the devastating tornadoes of this spring. Claims that global warming will cause more extreme weather events is a hypothesis, not an established fact, although you would not know that from some of the rhetoric.

Dr. Roy Spencer, a leading climate scientist from the University of Alabama, has studied the question about tornadoes by examining historical data. Data show that there has been a downward trend in strong (F3) to violent (F5) tornadoes in the U.S. since statistics began in the 1950s. This has also been a period of general warming. Obviously, the conclusion should be that warming causes fewer strong tornadoes, not more. That may seem counter-intuitive, but Dr. Spencer’s work shows the relationship between hurricanes and changes in the Pacific Decadal Oscillation (PDO), which he believes has a strong effect on temperature. A shift in the PDO earlier this decade has caused cooling not warming. Temperatures have not increased since 1998. Cool air over most of the US this spring has led to wind shears, which cause thunderstorms to rotate.

The climate system is very complex—too complex to captured by the assumed relationship between carbon dioxide emissions and temperature. We need more humility and less hubris in trying to understand our climate system and how human activities influence it. Predictions of accelerated warming and climate disasters that have been made over the past 22 years ultimately have to be confirmed or denied by facts. And the simple fact is that the predictions have not been borne out by the temperatures that we have actually experienced. Actual temperatures have been far less than model generated forecasts.