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.


July 11, 2012

What’s to Blame for the Rains on the Plains?

Filed under: Precipitation

The reigning myth has it that climate change from anthropogenic greenhouse gas (GHG) emissions is supposed to increase intense precipitation. But a slew of research now points to other causes for this. As a result, assessments of climate change, such as the one used by the EPA in support of its 2009 Endangerment Finding (which is required to justify proposed GHG emissions limits for U.S. power plants), may be wrong when they primarily blame changed rain intensity on GHGs.

Here is an example of how this plays out across the Heartland of the United States.


May 18, 2012

CO2 Not to Blame for Southwest Droughts?

Filed under: Floods, Precipitation

In our last WCR, we discussed a series of articles that found that higher resolution climate models—models which include a better representation of the complex terrain features of the Southwest—produce less drought stress on the Southwestern U.S. in their projections of future climate change from greenhouse gas emissions than do coarser resolution general circulation models.

Now comes along a new paper published in Nature magazine by Robert Allen and colleagues which suggests that the drying trend which remains is being caused more by black carbon aerosols and tropospheric ozone than by greenhouse gas emissions.


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.


March 12, 2012

Western U.S. Precipitation Extremes—How Did This Turkey Get Published?

When it comes to changes in future precipitation across the United States, climate models projections are all over the map. In other words, they provide no useful guidance for the future. But that doesn’t stop people from trying to sell them. Now comes a paper which clearly demonstrates a systematic failure of precipitation models and still calls the results “useful”. Reviewers…halloo??


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.


October 11, 2011

IPCC Mischaracterizes Precipitation Changes

Filed under: Precipitation

It it’s 2007 Fourth Assessment Report (AR4), the Intergovernmental Panel on Climate Change (IPCC) investigated the character of the changes in precipitation that have been observed across the world over the past half-century or so. In doing so, they concluded:

Observed changes in intense precipitation (with geographically varying thresholds between the 90th and 99.9th percentile of daily precipitation events) for more than one half of the global land area indicate an increasing probability of intense precipitation events beyond that expected from changes in the mean for many extratropical regions (Groisman et al., 2005; Figure 3.39, bottom panel). This finding supports the disproportionate changes in the precipitation extremes described in the majority of regional studies above, in particular for the mid-latitudes since about 1950.

Here’s the graphic mentioned in the quote above:

Figure 1. Bottom panel of IPCC AR4 Figure 3.39 showing “regions where disproportionate changes in heavy and very heavy precipitation during the past decades were documented as either an increase (+) or decrease (–) compared to the change in the annual and/or seasonal precipitation” (from IPCC AR4, 2007).

The problem is, is that the methodology that the IPCC relied upon was insufficient to base such a conclusion.

Over those regions where a more appropriate methodology has been employed, contrary to IPCC proclamations, the changes in intense precipitation events have proven to be very much proportionate to the observed changes in total annual precipitation. And even though the IPCC knew that this was the case for at least one of these major land areas (the United States), they nevertheless chose to forward the mischaracterization.

Chalk up another addition to the list of IPCC errors.


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 14, 2010

Raining on Boreal Forest Fires

Filed under: Climate Changes, Precipitation

No presentation on global warming is complete without images of some major wildfire – from day one, the global warming alarmists have insisted that a warmer world will generate more wildfires thereby devastating ecosystems from sea to shining sea. It is an easy sell – higher temperatures will increase potential evapotranspiration, forests dry out, and therefore become far more susceptible to fire. Recall that the entire global warming issue became front-page news back in 1988, and 1988 was the summer Yellowstone Park and much of the western United States suffered severe forest fires. Ever since, every major fire somehow gets linked to global warming. We searched the internet for “Fires and Global Warming” and found literally thousands of websites claiming that global warming will cause more fires, fires are causing global warming, and of course, global warming leaders should be fired!


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.


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