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The tropical lapse rate quandary

Filed under: — gavin @ 11 August 2005

Guest commentary by Steve Sherwood

There are four independent instrumental records of sufficient length and potential accuracy to tell us about 20th-century climate change. The two longest ones are of temperature near the Earth’s surface: a vast network of weather stations over land areas, and ship data from the oceans. While land surface observations go back hundreds of years in a few places, data of sufficient coverage for estimating global temperature have been available only since the end of the 19th century. These have shown about a 0.7 C warming over land during the last century, with somewhat less increase indicated over oceans. The land records contain artifacts due to things like urbanization or tree growth around station locations, buildings or air conditioners being installed near stations, etc., but laborious data screening, correction procedures, and a-posteriori tests have convinced nearly all researchers that the reported land warming trend must be largely correct. Qualitative indicators like sea ice coverage, spring thaw dates, and melting permafrost provide strong additional evidence that trends have been positive at middle and high northern latitudes, while glacier retreat suggests warming aloft at lower latitudes.

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Et Tu LT?

Filed under: — gavin @ 11 August 2005

In previous posts we have stressed that discrepancies between models and observations force scientists to re-examine the foundations of both the modelling and the interpretation of the data. So it has been for the apparent discrepancies between the Microwave Sounding Unit (MSU) lower tropospheric temperature records (MSU 2LT), radiosonde records and the climate models that try to simulate the climate of the last few decades. Three papers this week in Science Express, Mears et al, Santer et al (on which I’m a co-author) and Sherwood et al show that the discrepancy has been mostly resolved – in favour of the models.

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Storms & Global Warming II

Filed under: — rasmus @ 5 August 2005

Earlier this year, we posted two discussions on the association between climate change and storms: Storms and Climate Change and Some recent updates. I will use the abbreviation TC here in the loose meaning of a tropical cyclone. These posts discussed the high number of TCs during the previous hurricane season and an essay on the relation between TCs and climate change. The uncertainty surrounding trends in storminess was underlined, and a point was being made about this subject being controversial. More »

Did the Sun hit record highs over the last few decades?

Filed under: — group @ 3 August 2005

Guest commentary by Raimund Muscheler

[note: this is a restore (8/8/05) of an article from August 3, 2005 that was accidentally deleted due to a technical glitch. Unfortunately, most of the comments could not be retrieved. We sincerely apologize to our readers!]

The solar influence on climate is a controversial topic in climate research (see previous posts here and here). The irradiance changes are assumed to be relatively small and the importance of potential amplifying mechanisms is still a matter of current debate. One reason for these uncertainties is that there are only approximately 25 years of satellite-based observations of the solar irradiance. Sunspot observations for the last 400 years clearly indicate that current levels of solar activity are very different from the state of the sun during the Maunder minimum (from approx. 1645 to 1715 AD) where almost no sunspots could be observed.
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On record-breaking events

Filed under: — rasmus @ 1 August 2005

NASA’s Earth Observatory reports that there was a record low Arctic sea ice concentration in June 2005. There was a record-number of typhoons over Japan in 2004. In June, there were reports of a number of record-breaking events in the US. And on July 28, the British News paper The Independent reported on record-breaking rainfall (~1 m) in India, claiming hundreds of lives. These are just a few examples of recent observations. So, what is happening?

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