We are sure you have heard that global warming is causing more frequent and intense droughts throughout the world. Right? The claim is easy to make – higher temperatures increase evaporation rates, soil moisture is depleted, and drought conditions result. Indeed the Technical Summary of the most recent IPCC assessment includes “More intense and longer droughts have been observed over wider areas, particularly in the tropics and subtropics since the 1970s. While there are many different measures of drought, many studies use precipitation changes together with temperature. Increased drying due to higher temperatures and decreased land precipitation have contributed to these changes”. Further, they write “Although precipitation has increased in many areas of the globe, the area under drought has also increased. Drought duration and intensity has also increased. While regional droughts have occurred in the past, the widespread spatial extent of current droughts is broadly consistent with expected changes in the hydrologic cycle under warming. Water vapour increases with increasing global temperature, due to increased evaporation where surface moisture is available, and this tends to increase precipitation. However, increased continental temperatures are expected to lead to greater evaporation and drying, which is particularly important in dry regions where surface moisture is limited.” The bottom line in the table below from the IPCC’s Technical Summary leaves little doubt that the IPCC thinks that droughts have become more frequent, they have been caused in some part by humans, and they will become more frequent in the decades to come.

A major article on global-scale drought has appeared recently in the Journal of Climate by drought experts from Princeton University and the University of Washington; the work was supported by the U.S. Department of Energy the National Oceanic and Atmospheric Administration. We saw an interesting sentence in their abstract as Sheffield et al. wrote “Globally, the mid-1950s showed the highest drought activity and the mid-1970s to mid-1980s the lowest activity.” That does not seem consistent with the story coming from the IPCC.

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Of the many pillars that support the alarmist view of global warming is that droughts will increase in many parts of the world. This prediction is fairly straightforward, for if temperatures increase, potential evapotranspiration (ETo) should increase as well. If precipitation stays the same in the future and ETo increases with higher temperatures, the area would see a reduction in soil moisture and a trend toward drought. Of course should precipitation be reduced while ETo rates increase, the trend toward drought could be severe. In the ultimate alarmist view, ETo increase and extreme precipitation increases, and the area would then see an increase in both floods and droughts. We have heard it all before and we have covered these topics in many essays, but the beat goes on and on.

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Who could ever forget one of the opening scenes in The Day After Tomorrow when hailstones the size of basketballs were crashing into Tokyo causing death and destruction. Obviously, the greenhouse alarmists cannot wait to claim that severe storms will increase in frequency and intensity in the future, and nothing drives home the point like a city being punished by killer hail stones.

Amazingly, a search of “Global Warming and Hail” produces over one million hits, although some include the word “hail” as a word to “summon” or “call” for some action and have nothing to do with ice falling from the sky. Nonetheless, there is no end of material with titles about Nebraska towns using snowplows in summer to clear hail, crops being damaged by unusual hail events, and on and on. One of our favorites is “Latest Global Warming Worry: Megacryometeors” – use the word “megacryometeors” at the next greenie cocktail party and you will definitely win the award for outstanding global warming vocabulary!

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One claim from the global warming advocates we hear over and over is that severe storms are increasing in frequency and intensity. If pressed on this matter, they will concede that considerable debate surrounds trends or model predictions for hurricanes or tornados, but they insist that intense precipitation has definitely been increasing thanks to global warming. To buttress their arguments, they will point out that the Intergovernmental Panel on Climate Change (IPCC) states in their most recent summary that “The frequency of heavy precipitation events has increased over most land areas, consistent with warming and observed increases of atmospheric water vapour.” Furthermore, IPCC states that the observed trend over the most recent five decades is “likely,” that the trend is caused in some part by humans is “more likely than not,” and that the trend will continue this century is “very likely.”

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In nearly every presentation on global warming, we hear that floods and droughts will be more severe as the temperature rises. Believe it or not, and who would not believe it given thousands of websites on the issue, there are many scientists who believe the opposite. We have covered these topics in many previous essays, and a recent article in Quaternary Science Reviews reinforces our skeptical viewpoint.

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In the Wednesday December 5th, 2007 issue of the New York Times appeared a story by Felicity Barringer titled “Precipitation Across U.S. Intensifies Over 50 Years.” In it, Ms. Barringer reports on a new study released by an organization called Environment America that she described as “a national group that advocates new laws and policies to mitigate the effects of climate change.” The focus of the Environment America report was on the results of an analysis they performed examining trends in “extreme” precipitation frequency across the United States (apparently Environment America has spread these results to their arms in individual states, Environment Colorado, Environment California… you get the idea). The research was funded by the Pew Charitable Trusts. As Ms. Barringer reported, Environment America concluded that “Across the United States, the number of severe rainfalls and heavy snows has grown significantly in the last half-century, with the greatest increases in New England and the Middle Atlantic region” and, of course, that this was just as predicted to occur from global warming. Lest you think that more precipitation is a good thing, Environment America is quick to warn that “An increase in the frequency of storms delivering large amounts of rain or snow does not necessarily mean more water will be available” and that “[w]hile it may seem like a paradox, scientists expect that extreme downpours will be punctuated by longer periods of relative dryness, increasing the risk of drought.”

That the New York Times chose to highlight the Environment America report is interesting for a number of reasons, among them: 1) the report did not appear in the scientific literature (rather it was released by an environmental organization), 2) a day prior to the Times article, a paper was published in the peer-reviewed scientific literature which concluded that “extreme” precipitation was increasing across the United States (but no mention of it was made by Ms. Barringer), and 3) a paper published in the peer-reviewed scientific literature back in 2004, also described increases in “extreme” precipitation events across the United States, but also cautioned that based upon the nature of precipitation, increases in precipitation amounts are virtually always accompanied by apparent increases in “extreme” precipitation events and thus singling out “extreme” precipitation events without discussing overall precipitation trends is alarmist by its very nature. Oh, we forgot to mention, that the two papers in the scientific literature that found increases in extreme precipitation across the U.S. included among their co-authors some folks often deemed industry-funded global warming skeptics (Brommer, Cerveny, Balling, 2007; Michaels, Knappenberger, Frauenfeld, Davis, 2004). Perhaps our papers didn’t warrant coverage in the Times because we failed to include breathless prose about how global warming was to blame, or perhaps because we failed to outline steps that should be taken to reduce carbon dioxide emissions, or maybe we didn’t time the release of our papers to coincide with a major international meeting on climate change (although one of them was published by chance this week). Or maybe, it was that pointing out that the basic findings by some global warming “skeptics” closely matched that from “concerned” environmental organizations would take all the fun out of vilifying the skeptics, so it was best to simply ignore them to avoid the awkwardness altogether.

A closer look at the Environment America paper clearly shows it to be the inferior of the three papers—at least if scientific significance is the standard by which it is judged. If global warming alarmism is deemed the most important attribute, well, then there is no contest.

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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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