According to 1,000s of websites trumpeting the horrors of global warming, we find countless claims that the ongoing build-up of greenhouse gases is causing droughts and floods all over the world. Hardly a week goes by nowadays without a front page news story about some weather or climate calamity occurring somewhere on the planet, and global warming is repeatedly claimed to be the cause. Turn the radio to NPR for an hour or so, and you will certainly be told how the failure of the United States to sign the Kyoto Protocol has caused some disastrous flood or drought.

Several articles have been published recently allowing us to catch a glimpse of centuries of climate variations in China, and as we have seen in hundreds of other similar studies, nothing all that unusual has been happening lately. The first of these recent articles will soon appear in Climate Dynamics and was written by the team of Shen, Wang, Hao, and Gong of the Atmospheric Sciences Research Center of the State University of New York. They note that “In recent decades, eastern China has suffered increased droughts in its north and increased floods in its south. The studies of climate models suggested that this trend could probably be attributed to the climate effects of black carbon aerosols and human-induced land cover changes”. Holy smokes – black carbon and land use? Shen et al. apparently haven’t been listening to enough NPR for surely drought and floods in China are related to global warming!

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Have you been hearing a lot about drought recently? Or maybe you’ve been hearing a lot about flooding recently? Probably depends on where you live. The map below (Figure 1) shows the current state of drought (and extreme moisture) across the United States as of a few days ago, and the map shows “Extreme Drought” in much of the American West (a pattern that extends well into Canada), “Extreme Drought” in the Southeast, but “Extreme Moist” conditions in Texas and parts of the middle of the country. Add in some record-breaking high temperatures in October in the Northeast, and the global warming crowd is once primed to blame everything you see on the dreaded build-up of greenhouse gases. This week, we even learned that the fashion industry is gearing up for a world with milder winters, orangutans are feeling the heat, presidential hopefuls are pledging to do something about the changing climate, and who knows what else?

Figure 1. Moisture status across the United States.

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For decades, climate scientists have run numerical experiments to predict the climate response to the buildup of greenhouse gases and the answer consistently falls on the side of warming on the global scale. The climate models have become more sophisticated by orders of magnitude over the past 40 years, and the prediction of warming given increased concentrations of greenhouse gases remains as the central pillar in the global warming issue. The fact that the Earth has warmed over the past three decades makes it very easy to claim that greenhouse gases are increasing, models predict warming, the Earth’s temperature is increasing, and therefore, the science debate on the issue is over.

We at World Climate Report have confessed repeatedly that some part of the observed warming over the past three decades is very likely related to the ongoing buildup of greenhouse gases. However, thousands (actually, millions on the internet) of presentations on global warming feature claims that climate models are predicting more floods, more droughts, more hurricanes, more glacial melting, more sea level rise, more species extinctions, more … anything you can possibly name (assuming what you name is potentially catastrophic). Our essays repeatedly show that (a) models really don’t make such predictions, (b) models are not capable of such predictions, and/or (c) there is no evidence that such predictions are supported by observational data.

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There is little doubt that increasing atmospheric concentrations of greenhouse gases will generally cause the Earth to warm and alter precipitation patterns in various parts of the globe. Changes in precipitation and temperature will thereby impact hydrological systems, and the global warming alarmists love to show images of floods or dried-up streams to make the threat of the anthropogenic greenhouse effect look as bad as possible. Indeed, the global warming scare has deep roots in the drought of 1988 over the southeastern United States that created an anomalous low flow on the Mississippi River (recall headlines about the Mississippi River drying up?). If you have forgotten, the summer of 1988 also gave us the huge wildfires of the West (Yellowstone Park burned in that summer and fall) as well as Hurricane Gilbert, and those images of how global warming will impact us have lived on powerfully ever since.

The literature on how the enhanced greenhouse effect will alter streams and rivers shows us everything from floods to record-breaking low flows, and of course, both will be bad for humans and natural ecosystems. Floods are definitely bad, but in low flow situations, agriculture will be severely impacted, direct human use of water would need to be curtailed, and if the stream provides hydropower, the impacts can be severe in the energy sector.

Canada is a mid-to-high latitude, northern hemispheric land mass where global warming is expected to be far greater than in other parts of the world, and this warming will surely be felt by the streams across their country. An article has appeared in a recent issue of Journal of Hydrology entitled “Streamflow in the Winnipeg River Basin, Canada: Trends, Extremes and Climate Linkages” by Scott St. George of the Geological Survey of Canada and the University of Arizona. The final sentence of the abstract caught our eye as he wrote “the potential threats to water supply faced by the Canadian Prairie provinces over the next few decades will not include decreasing streamflow in the Winnipeg River basin.” We knew immediately that we had a Winnipeg winner on the line! Let the world know that funding for his work was provided by Manitoba Hydro, the Manitoba Geological Survey, the Prairie Adaptation Research Collaborative and the Natural Sciences and Engineering Research Council of Canada.

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Wildfires have been associated with the global warming scare for decades, and nearly two million websites found for “Forest Fires and Global Warming” continue to stoke the flames. The argument seems rather simple – the world warms and in the absence of a compensating increase in precipitation, many areas of the world become drier. The drier vegetation is more vulnerable to fires, and more wildfires result. A few pictures of Yellowstone Park and/or San Diego hillsides on fire will help make the point. Add comments about how vegetation is stressed trying to cope with rapid environmental change, and fires seem even more inevitable. Furthermore, a not-so-complicated set of feedbacks can make it seem even worse – note that fires contribute enormously to the atmospheric carbon dioxide concentration and then describe how a darker surface resulting from fires can decrease the reflectivity of the surface (making it as black as a parking lot) thereby resulting in even more warming. Given that wildfires are impacting some part of the Earth every day, there is no end to up-to-date photo opportunities, there are plenty of folks are willing to speculate that “we may be seeing the impacts of climate change,” and a pillar of the greenhouse earth is reinforced. Through in some heart-wrenching pictures of animals coping with a burned forest or grassland, and to say the least, you are part of the global warming fraternity.

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Since the first time you heard about global warming, you probably learned that among other consequences, wildfires will increase in frequency and area burned in many parts of the world. This prediction is based on the obvious link that increased temperatures will increase evapotranspiration, forests will become drier in the absence of any increase in precipitation, the changes in climate will promote a weakening of the forest ecosystems making them more susceptible to countless stresses, and forests will “burn baby burn.” Back in 1988 when the greenhouse engine was getting into gear (a rather low gear compared to the overdrive gear of today), Yellowstone Park burned as did many other forests in the western states, and the image of forest fires being linked to global warming has lived on ever since. There is not a day that a substantial forest fire is not burning somewhere across the planet, so the popular press will never run out of material on this front.

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We have been told over and over that the buildup of greenhouse gases will vastly alter climate all over the world. The planet will be warmer, precipitation will be greater, droughts and floods will savage civilization, and everything will be worse than we could ever believe. In the case of the central United States, we have been warned repeatedly that higher atmospheric concentrations of greenhouse gases will lead to a substantial increase in the duration, severity, and areal extent of droughts in the American heartland.

A recent issue of Geophysical Research Letters includes two articles that shed light on the future (and past) of droughts in the central United States. The first article was produced by five climatologists from academic units at Purdue, Minnesota, Wisconsin, and Oregon. Diffenbaugh et al. focused on the Mid-Holocene period between 8,000 and 3,000 years ago — a period for which the proxy record clearly shows drier-than-present conditions throughout the central United States. They note that “Proxy data also indicate that changes in summer precipitation played a major role in shaping mid-Holocene moisture balance in North America.” Back then, summers were a lot drier than today, despite any lack of elevated concentration of greenhouse gases.

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Glacier National Park just seems to come up repeatedly in the debate about global warming. This poster child of the greenies is sacred ground, for it provides an opportunity to show the kids where the glaciers were when you were a kid, see where the glaciers terminate today, and of course blame global warming and further blame the Bush Administration for not signing the Kyoto Protocol. Many documentaries on the greenhouse effect have been drawn to the Park, and if you Google “Glacier National Park and Global Warming,” you will be directed to approximately 159,000 sites.

A very interesting paper on Glacier National Park appears in a recent issue of Earth Interactions by scientists at Montana State University and the U.S. Geological Survey. Pederson et al. begin their article noting that “Evidence from an increasingly rich paleoproxy record demonstrates that over the last millennium decadal to multidecadal precipitation anomalies have been a substantial, if not defining, component of western North America’s climates. As in the twentieth century, the last 1000 yr has experienced sporadic episodes of both persistent (>10 yr) droughts and wet regimes, though the magnitude and duration of many paleodroughts surpass those captured by the instrumental record.” The notion that droughts in the past were far worse than any recent drought brought our attention to the article, but there is far more to the story than just past droughts.

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A recent article in Geophysical Research Letters by Rutgers’ scientists Alan Robock and Haibin Li addresses the issue of global warming and reduced soil moisture levels in important agricultural areas. Every popular global warming presentation lays out the case that higher temperatures in the future will cause higher levels of evaporation that will overwhelm any changes in precipitation and force soil moisture levels to drop. Of course, crops will fail, we will have more frequent and severe droughts of longer duration, and it will have all been caused by elevated carbon dioxide (CO2) levels. You’ve heard the story a 1,000 times by now.

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We have all heard the news that droughts will certainly become longer, more frequent, and more severe thanks to global warming. Higher temperatures will surely increase rates of potential evapotranspiration, and even if precipitation patterns remain unchanged, the odds will favor more droughts in the future. The Intergovernmental Panel on Climate Change (IPCC) states in the 2001 Summary for Policymakers that it is “Likely” that “Increased summer continental drying and associate risk of drought” has occurred in the later half of the 20th century and “Likely, over most mid-latitude continental interiors” to occur during the 21st century.

Figure 1 below shows the current state of affairs as of November 4, 2006, and generally, widespread drought in the mid-latitude continental interior is absent. In fact, as we look at the Great Plains, we find more areas in the “Extremely Moist” category than the “Extreme Drought” category. We would all agree that one snapshot of soil moisture conditions in the United States is not an adequate way to test the idea that global warming will lead to an increase in drought in mid-latitude continental interiors. What is needed, of course, is a longer perspective with drought information over hundreds of years.

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