AGW Observer

Observations of anthropogenic global warming

New research from last week 43/2010

Posted by Ari Jokimäki on November 1, 2010

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as I write them. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

Massive methane release from seafloor recently near Japan

Bangs et al. found a V-shaped recently eroded depression from seafloor offshore southwestern Japan. UPDATE (November 1, 2010): Kees van der Leun just informed me (thanks! :) ) – after asking Nathan Banks about this – that “recently” here means about 40,000 to 50,000 years ago.

“The shape of the relic BSR indicates that the seafloor depression was once a large anticline that has recently been eroded and released an estimated 1.51 × 1011 m3 of methane.”

One possible explanation for the release is that bottom-water currents might have caused erosion and eventually revealed methane hydrates.

“Once triggered, gas-driven erosion created a positive feedback mechanism, releasing gas and eroding hydrate-bearing sediment. We suggest that erosive currents in deep-water methane hydrate provinces act as hair triggers, destabilizing kilometer-scale swaths of the seafloor where large concentrations of underlying overpressured methane exist.”

Citation: N.L. Bangs, M.J. Hornbach, G.F. Moore, and J.-O. Park, Massive methane release triggered by seafloor erosion offshore southwestern Japan, Geology, 2010, v. 38 no. 11 p. 1019-1022, doi: 10.1130/G31491.1. [abstract]

New review article on sun’s effect to climate

New review article looks at the current state of research on sun’s effect to climate. General conclusion on the recent climate change is that while sun obviously affects Earth’s climate in many ways, anthropogenic forcing is required to explain the warming in last few decades. On cosmic rays:

“We therefore conclude that the currently available data do not provide substantial support for the hypothesized global cloud cover linkage to cosmic rays.”

Citation: Gray, L. J., et al. (2010), SOLAR INFLUENCES ON CLIMATE, Rev. Geophys., 48, RG4001, doi:10.1029/2009RG000282. [abstract, full text]

Thousand-year drough reconstruction from Unites States

New research article describes a 1000-year drought reconstruction using subfossil oak tree-rings from central United States. Driest year during the instrumental record (after 1895) was 1934 but before instrumental record there were three years that were even drier.

“Thirteen decadal to multidecadal droughts (i.e., ≥10 years) occurred during the last millennium – the longest lasting sixty-one years and centered on the late twelfth century.”

There were also some signs of periodicity:

“Reconstructions exhibited quasi-periodicity at bidecadal and century-scale periods. Significant rhythms in drought were identified near 20-yr and 128-yr periods.”

Citation: Michael C. Stambaugh, Richard P. Guyette, Erin R. McMurry, Edward R. Cook, David M. Meko, and Anthony R. Lupo, Drought duration and frequency in the U.S. Corn Belt during the last millennium (AD 992–2004), Agricultural and Forest Meteorology, doi:10.1016/j.agrformet.2010.09.010. [abstract]

How much should the public know about climate science?

Just published editorial comment in Climatic Change discusses “How much should the public know about climate science?” But discusses at the same time also some basics of climate science.

“The greenhouse effect is well understood. It is as real as gravity. The foundations of the science are more than 150 years old. Carbon dioxide in the atmosphere traps heat. We know carbon dioxide is increasing because we measure it. We know the increase is due to human activities like burning fossil fuels because we can analyze the chemical evidence for that.”

Citation: Richard C. J. Somerville, How much should the public know about climate science?, 2010, Climatic Change, DOI: 10.1007/s10584-010-9938-y. [abstract, full text]

When will the Arctic be free of sea-ice?

Numerical experiments are used in a new study to estimate the timing of ice-free Arctic with different amounts of anthropogenic warming and climate variability. If surface temperature increase is 4°C and climate variability is similar to past two decades, the ice-free state is likely reached by mid-2040′s. If surface temperature increase is 2°C with same variability, the ice-free state is unlikely before 2050. If surface temperature is 4°C and climate variability is similar to past five decades, the ice-free state also is unlikely before 2050. They mention an interesting negative feedback for volume loss:

“The rate of annual mean ice volume decrease relaxes approaching 2050. This is because, while increasing SAT increases summer ice melt, a thinner ice cover increases winter ice growth. A thinner ice cover also results in a reduced ice export, which helps to further slow ice volume loss.”

Citation: Zhang, J., M. Steele, and A. Schweiger (2010), Arctic sea ice response to atmospheric forcings with varying levels of anthropogenic warming and climate variability, Geophys. Res. Lett., 37, L20505, doi:10.1029/2010GL044988. [abstract]

In Hong Kong modern times are hotter and wetter

Extreme temperatures and rainfall from 1885 to 2008 in Hong Kong were analysed in a new study.

“Results showed that the extreme daily maximum and minimum temperatures, annual numbers of very hot days (daily maximum temperature ≥ 33.0 °C) and hot nights (daily minimum temperature ≥ 28.0 °C) as well as the warm spell duration index (WSDI) in Hong Kong exhibited statistically significant long-term rising trends, whereas the annual number of cold days (daily minimum temperatures ≤ 12.0 °C) and cold spell duration (CSDI) index had a statistically significant decreasing trend.”

Both extreme rain and annual precipitation also increased significantly. However, the dry spell in summer months also got little longer.

Citation: M. C. Wong, H. Y. Mok, T. C. Lee, Observed changes in extreme weather indices in Hong Kong, International Journal of Climatology, 2010, DOI: 10.1002/joc.2238. [abstract]

Cereal production in Russia might not benefit from climate change after all

Climate change is generally thought to improve the agriculture in North. A new study has found out that this might not be so:

“We analyzed the impact of climate change on production of cereals in Russia and found that this general perception of beneficiary effect of a warmer climate is unlikely to hold, primarily due to increasing risk of droughts in the most important agricultural areas of the country.”

Citation: Nikolai Dronin and Andrei Kirilenko, Climate change, food stress, and security in Russia, Regional Environmental Change, DOI: 10.1007/s10113-010-0165-x. [abstract]

New paper claims there’s not much empirical evidence for AGW

A new study claims:

“At best, the empirical evidence for human impact on climate change, more specifically, the anthropogenic global warming (AGW), is based on correlational research”

Study concentrates on the details of correlational research. There’s some very questionable remarks in the paper, for example this one:

“Unfortunately, when a theoretical phenomenon such as AGW becomes a global political program, it soon becomes vulnerable to methodological fallacies in the realm of social and political science.”

However, above claims are largely left unproven (there’s no empirical evidence review at all in the paper), but it is mentioned that:

“However, since the author of this article is no expert on climate science, the issue of whether or not data used in climate science are of enough quality will be left for others to decide.”

The references in the paper relating to climate science are mostly known denier papers.

Citation: Jarl K. Kampen, A methodological note on the making of causal statements in the debate on anthropogenic global warming, Theoretical and Applied Climatology, DOI: 10.1007/s00704-010-0355-y. [abstract, full text]

Groundwater is diminishing globally and causing sea-level rise

A new study gives an overview of groundwater depletion. Groundwater recharge was estimated with a hydrological model and groundwater abstraction estimates were subtracted from recharge estimates. Mankind uses groundwater especially in places where other water sources are not present. The results:

“Restricting our analysis to sub-humid to arid areas we estimate the total global groundwater depletion to have increased from 126 (±32) km3 a-1 in 1960 to 283 (±40) km3 a-1 in 2000. The latter equals 39 (±10)% of the global yearly groundwater abstraction, 2 (±0.6)% of the global yearly groundwater recharge, 0.8 (±0.1)% of the global yearly continental runoff and 0.4 (±0.06)% of the global yearly evaporation, contributing a considerable amount of 0.8 (±0.1) mm a-1 to current sea-level rise.”

Citation: Wada, Y., L. P. H. van Beek, C. M. van Kempen, J. W. T. M. Reckman, S. Vasak, and M. F. P. Bierkens (2010), Global depletion of groundwater resources, Geophys. Res. Lett., 37, L20402, doi:10.1029/2010GL044571. [abstract]

Tropospheric humidity drop reveals surface warming

Radiosonde humidity resords have been analysed in a new study. It is a general expectation that tropospheric humidity increases with surface warming. According to observations, tropopause is going higher. These both are shown also in this new study. However, there was a surprise:

“The most remarkable finding of this trend analysis is a significant drop in upper tropospheric humidity (UTH) around autumn 2001, which marks an end to the upper tropospheric moistening of the precedent decade. This UTH drop in autumn 2001 coexists with a sudden lifting and cooling of the tropopause and with a significant stretch-out of the free troposphere. Therefore, we conclude that these autumn 2001 trends are certainly associated with the dynamical behavior of the troposphere, triggered by the surface warming.”

Citation: Van Malderen, R., and H. De Backer (2010), A drop in upper tropospheric humidity in autumn 2001, as derived from radiosonde measurements at Uccle, Belgium, J. Geophys. Res., 115, D20114, doi:10.1029/2009JD013587. [abstract]

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