February 26, 2010

Quick Response to Ben Santer’s Comments at RealClimate

Ben Santer has an article over at RealClimate defending himself against some claims made recently by Fred Pearce in a series of articles Pearce did for the U.K.’s Guardian in recent weeks.

In particular, Santer discusses a 1996 paper that he (and colleagues) published in Nature magazine in which they reported to have identified a human fingerprint on global temperature change. Well, actually, in his RealClimate article Santer primarily discusses his Response to a Comment that WCR’s Patrick Michaels and Chip Knappenberger published in Nature that pointed out that had Santer et al. used the full observational period of record available at the time they published their original paper (instead of a truncated one), that Santer et al.’s statements “about the strength of the evidence for human alteration of the lower tropospheric climate must be tempered.”

In Santer’s RealClimate piece, he claims that in his Response to our Comment, that he “demonstrated that this criticism was simply wrong.” And that “[u]se of a longer record of atmospheric temperature change strengthened rather than weakened the evidence for a human fingerprint.”

At RealClimate, Santer provided this link to his Response to our Comments. Here, for completeness’s sake, we provide a link to our Comment.

We invite you to read them both and see for yourself.

Personally, we are incredulous that Santer maintains, even to this day, that had they used the full period of available record—which he admits would have shown a decline in the correlation between models and observations—that this somehow “strengthened rather than weakened the evidence for a human fingerprint.”

We can only wonder what he would have concluded had the full dataset of observations maintained or strengthened his original correlation! Somehow we doubt that had the updated data strengthened the correlation between models and observations, that Santer would have come out and declared this as evidence the human fingerprint was fading.

(There is lots more regarding this issue (and others discussed by Santer in his RealClimate article) that resides in our back pages. To investigate for yourself, use our ‘back issues’ search function and enter “Santer”)

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.


February 16, 2010

Another IPCC Error: Antarctic Sea Ice Increase Underestimated by 50%

Filed under: Antarctic, Climate Changes

Several errors have been recently uncovered in the 4th Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC). These include problems with Himalayan glaciers, African agriculture, Amazon rainforests, Dutch geography, and attribution of damages from extreme weather events. More seem to turn up daily. Most of these errors stem from the IPCC’s reliance on non-peer reviewed sources.

The defenders of the IPCC have contended that most of these errors are minor in significance and are confined to the Working Group II Report (the one on impacts, adaptation and vulnerability) of the IPCC which was put together by representatives from various regional interests and that there was not as much hard science available to call upon as there was in the Working Group I report (“The Physical Science Basis”). The IPCC defenders argue that there have been no (or practically no) problems identified in the Working Group I (WGI) report on the science.

We humbly disagree.


February 9, 2010

GPS Aids in Sea Level Rise Debate

The Technical Summary of the most recent IPCC reports states that “Over the 1961 to 2003 period, the average rate of global mean sea level rise is estimated from tide gauge data to be 1.8 ± 0.5 mm yr–1.” “The average thermal expansion contribution to sea level rise for this period was 0.42 ± 0.12 mm yr–1, with significant decadal variations, while the contribution from glaciers, ice caps and ice sheets is estimated to have been 0.7 ± 0.5 mm yr–1. The sum of these estimated climate-related contributions for about the past four decades thus amounts to 1.1 ± 0.5 mm yr–1, which is less than the best estimate from the tide gauge observations. Therefore, the sea level budget for 1961 to 2003 has not been closed satisfactorily.”

That is indeed very interesting – the average rate of sea level is around 1.8 mm per year, and the IPCC can account for only 60% of the increase. This uncertainty is compound considering IPCC’s statements that “The global average rate of sea level rise measured by TOPEX/Poseidon satellite altimetry during 1993 to 2003 is 3.1 ± 0.7 mm yr–1. This observed rate for the recent period is close to the estimated total of 2.8 ± 0.7 mm yr–1 for the climate-related contributions due to thermal expansion (1.6 ± 0.5 mm yr–1) and changes in land ice (1.2 ± 0.4 mm yr–1). Hence, the understanding of the budget has improved significantly for this recent period, with the climate contributions constituting the main factors in the sea level budget (which is closed to within known errors). Whether the faster rate for 1993 to 2003 compared to 1961 to 2003 reflects decadal variability or an increase in the longer-term trend is unclear”.

As you might guess, there is much to be done to improve our understanding of sea level rise.


February 1, 2010

What’s Happened to Global Warming?

One of the enduring pillars of the climate change issue is that the temperature of the Earth is increasing at an unprecedented rate … we’ve heard it a million times over the past few decades. However, it is well known that the temperature of the Earth has not increased over the past decade, and the lack of recent warming is now receiving serious consideration in the leading scientific journals. Two recent articles are of particular interest to us at World Climate Report.


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