August 14, 2012

Hansen Is Wrong

Filed under: Droughts, Precipitation

In his recent press blitz, NASA’s James Hansen tries to tie extreme weather events, such the current drought affecting much of the central U.S., to anthropogenic global warming. But the real world argues otherwise.

Hansen is quite adept at timing global warming pronouncements with extreme weather events. Recall that it was during a similar hot, dry period back in the summer of 1988 that Hansen first testified to Congress that global warming from human greenhouse gas emissions was impacting current weather events—testimony which many credit as giving rise to the global-warming-is-going-to-be-bad movement. But then, as now, the tie-in between weather events and human changes to the atmospheric greenhouse effect is tenuous at best, and tie-ins to specific events are ill-supported and ill-advised. In the best case, the anthropogenic emissions-driven rise in global temperatures has a small ancillary impact on a specific extreme weather event, but in the vast majority of the cases, its role is nugatory and undetectable.


May 14, 2012

Future Southwest Drought in Doubt?

Filed under: Droughts, Precipitation

One of the most “robust” signals from global climate models run under scenarios of increasing human greenhouse gas emissions is an even drier climate in the Southwestern U.S. than exists there currently.

The 2009 report “Global Climate Change Impacts in the United States” from the U.S. Global Change Research Program (a report which the EPA relied upon in making its “Endangerment Finding” from carbon dioxide and other greenhouse gases) has this to say about the prospects of future drought in the U.S. (p. 33):

“In the future, droughts are likely to become more frequent and severe in some regions. The Southwest, in particular, is expected to experience increasing drought as changes in atmospheric circulation patterns cause the dry zone just outside the tropics to expand farther northward in the United States.”

The 2007 Fourth Assessment Report of the IPCC (another report which the EPA relied heavily upon in making its “Endangerment Finding”) had this to say (p. 890):

“Annual mean precipitation is very likely to increase in Canada and the northeast USA, and likely to decrease in the southwest USA.”

Not surprisingly, the EPA included this statement about projected changes in precipitation in the Executive Summary of its Technical Support Document for its “Endangerment and Cause or Contribute Findings for Greenhouse Gases under Section 202(a) of the Clean Air Act”:

“Increases in the amount of precipitation are very likely in higher latitudes, while decreases are likely in most subtropical latitudes and the southwestern U.S., continuing observed patterns.”

But new research published in Geophysical Research Letters suggests that the USGCRP, the IPCC, and consequently, the EPA may be overdoing things a bit.


January 30, 2012

The Problem with Proxies

Filed under: Droughts, Precipitation

There is a new paper (in press in the journal Geophysical Research Letters) that presents a lesson that we all should keep in mind—results based on reconstructions of climate phenomena that are based on once or twice removed “proxy” indicators, may not be as reliable as they appear (or as they are presented) to be. If this brings hockey sticks and salacious emails to mind, you are not alone.

“Proxies” are putative indicators of climate for which there are no direct measurements. Tree rings, for example, are wider when the summer is wet and not too hot. The actual “explained variance” between them and, say, annual temperature is complex to derive and not all that high. The same is true for most other types of proxies (e.g., corals, ice cores, lake sediments, stalagmites, boreholes, etc.). Therefore, the uncertainties in using proxies to “reconstruct” some aspect of the climate are typically large (certainly larger than typically portrayed) and making (robust) conclusions from such analyses becomes a bit tricky. Such problems are among the reasons that many people jumped all over Michael Mann’s infamous “hockey stick” reconstruction of climate, which claims to accurately represent annual temperatures on a year-to-year basis back some 1000 years. Lesson: be very careful with proxy climate data.

Today’s example involves wildfire occurrence in the western U.S., and the climate patterns that may influence it.


August 25, 2010

Southwest Drought?

Filed under: Droughts, Precipitation

As we have covered in previous essays, global warming alarmists insist that the southwestern United States is getting drier and will get substantially drier in the future due to the buildup of greenhouse gases. They bolster their claims by results from a relatively large number of articles in the professional scientific literature and countless comments in various UN IPCC reports. Throw in pictures of declining water levels at Lake Mead, some fountains in Las Vegas and golf courses in Phoenix, and just like magic, a scary scenario is produced.

As with virtually every other element of the climate change issue, the literature produces some surprises, and the drought in the Southwest claim runs up against some interesting realities. The latest article on this subject appears in a recent issue of the Journal of Geophysical Research and once again, the results are at odds with the popular perception of increased drought in the Southwest.


June 3, 2010

Leave it to Beavers

In recognition of the recent discovery of the world’s largest beaver dam, we take a look into the activities of past beavers to see what they may be able to tell us about previous climate changes, and we speculate on the impacts that on-going climate changes may be having on the likes and dislikes of current beavers.

World’s largest beaver dam in found in Northern Alberta, Canada.


May 11, 2010

Pan Paradox

Filed under: Droughts, Precipitation

One of the ongoing debates in the climate change world involves the popular prediction of more droughts, longer droughts, and droughts of greater intensity. The underpinnings of this prediction are easy to follow, so this is definitely a strong pillar in the climate alarmist camp. As the temperature increases, potential evapotranspiration (PET) will certainly increase. There are many equations describing the relationship between PET and temperature, and they all indeed show PET would increase should the temperature increase. The physics here is solid. So if PET increases, actual evaporation will increase in areas with even a small amount of soil moisture, and in the absence of some compensating increase in rainfall, soil moisture will be depleted. The combination of increasing temperatures and decreasing precipitation should all but guarantee the place will become drier thereby yielding the increase in drought duration, intensity, and frequency. There is always a drought somewhere on the planet to point to as evidence that this is really happening, will likely get worse in the future, and all the rest. We’ve all heard it a million times … “If we don’t act know, ______ will happen” (fill in the blank, but today, we will focus on droughts).


April 19, 2010

Amazing Amazon Analysis

Filed under: Droughts, Floods, Precipitation

If you really want to hit a home run with a global warming story, manage to link climate change to the beloved rainforest of the Amazon. The rainforest there is considered by many to be the “lungs of the planet,” the rainforest surely contains a cure for any ailment imaginable, all species in the place are critical to the existence of life on the Earth, and the people of the Amazon are surely the most knowledgeable group on the planet regarding how to care for Mother Earth.

The global warming alarmists have taken full advantage of the Amazon and they are very quick to suggest that the Amazon ecosystem is extremely sensitive to climate change. Furthermore, not only can climate change impact the Amazon, but global climate itself is strongly linked to the state of the Amazon rainforest.

But, as usual, there is more to this story than meets to eye (or, rather, the press).


February 24, 2010

Update on Global Drought Patterns (IPCC Take Note)

Filed under: Droughts, Precipitation

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.


January 20, 2010

Hydrocycle Looking Better than Ever

Filed under: Droughts, Floods, Precipitation

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.


April 24, 2008

Floods and Droughts and Global Cooling?

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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