AGW Observer

Observations of anthropogenic global warming

New research from last week 44/2010

Posted by Ari Jokimäki on November 8, 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:

Man-made increase in GHG’s changes North Atlantic Oscillation (NAO) through stratosphere

Changes have been observed in NAO: NAO action centres have moved eastward, zonal wind anomalies have moved poleward, and NAO climate anomalies have extended “downstream”. A new study has used climate models to investigate these changes and their causes. It is found that the increase in atmospheric carbon dioxide and the increase in sea surface temperature both can cause the observed effects. When SST causes the changes, it is through tropospheric dynamics. However, the increase in carbon dioxide affects in other way – it has to do with changes in stratosphere:

“However, there is a significant response in the stratosphere, characterized by a strengthened climatological polar vortex with strongly enhanced interannual variability. … The similarity of changes in many characteristics of NAO interannual variability between the model response to doubling CO2 and those in observations in the mid-1970s implies that the increase of greenhouse gas concentration in the atmosphere, and the resulting changes in the stratosphere, might have played an important role in the multidecadal change of interannual NAO variability and its associated climate anomalies during the late twentieth century.”

Citation: Buwen Dong, Rowan T. Sutton and Tim Woollings, Changes of interannual NAO variability in response to greenhouse gases forcing, Climate Dynamics, DOI: 10.1007/s00382-010-0936-6. [abstract]

Different snow volume trends in Eurasia and North America

Measurements from satellites were used to evaluate changes in snow volume in northern high latitudes except Greenland in a new study. The study found a differing trends from Eurasia and North America:

“While the snow volume exhibits a statistically significant negative trend (-9.7±3.8 km3.year-1, p-value=0.02) over North America, it presents a positive, but not statistically significant trend (11.3±9.3 km3.year-1, p-value=0.25) over Eurasia.”

The reason for different trends probably is found from differences in regional climates. In Eurasia the snow volume is related to Arctic Oscillation and Atlantic Multidecadal Oscillation (AMO) while in North America it is related to Pacific North American pattern and AMO.

Citation: Sylvain Biancamaria, Anny Cazenave, Nelly M. Mognard, William Llovel and Frédéric Frappart, Satellite-based high latitude snow volume trend, variability and contribution to sea level over 1989/2006, 2010, Global and Planetary Change, doi:10.1016/j.gloplacha.2010.10.011. [abstract]

Fish populations track climate patterns in San Francisco Bay

San Francisco Bay fish and invertebrates have been followed since 1980 which shows that there are large changes in the populations. One particularly dramatic change occurred in 1999 when Pacific Decadal Oscillation (PDO) and North Pacific Gyre Oscillation (NPGO) reversed their signs. The conclusion of the study:

“We infer that synchronous shifts in climate patterns and community variability in San Francisco Bay are related to changes in oceanic wind forcing that modify coastal currents, upwelling intensity, surface temperature, and their influence on recruitment of marine species that utilize estuaries as nursery habitat.”

What I find interesting here is that the species seem to react surprisingly strongly to changes in climate. I would have thought that most of the species are not affected by very brief changes in climate. For example one could imagine that fish communities would be used to oscillations in the ocean currents but here it seems that even short time natural variability causes rather dramatic changes in the populations of species.

Citation: Cloern, J. E., et al. (2010), Biological communities in San Francisco Bay track large-scale climate forcing over the North Pacific, Geophys. Res. Lett., 37, L21602, doi:10.1029/2010GL044774. [abstract]

Global brightening caused by aerosols – not clouds?

A new research article describes studies on the global brightening issue. Abstract is short so it’s quoted here in full:

“Solar radiation at the Earth surface has increased over land and ocean since about 1990 (‘global brightening’). An analysis of various global (ocean only) aerosol and (global) cloud data sets from geostationary and polar orbiting satellites is performed to determine whether changes in these quantities have occurred in accordance with ‘global brightening’, and to analyse the global distribution of these changes. Change-point detection and trend analysis are employed in the analysis. In a period from the mid-1980s to the mid-2000s, aerosol optical depth is found to have started declining in the early 1990s, while cloud data sets do not agree on trends. Ångström exponent data seem to suggest changes in pollution.”

Citation: Cermak, J., M. Wild, R. Knutti, M. I. Mishchenko, and A. K. Heidinger (2010), Consistency of global satellite-derived aerosol and cloud data sets with recent brightening observations, Geophys. Res. Lett., 37, L21704, doi:10.1029/2010GL044632. [abstract]

New review article on climate science and social movement

New review paper traces the history of climate change knowledge and social movement:

“This article reviews relevant studies and theories of social movements with special attention to the role of knowledge-making in social movements, before tracing the relations between social movements and climate change knowledge from the 1970s to the present. Climate change first emerged as an issue of public concern within the context of the environmental movements of the 1970s and 1980s, while skepticism was shaped, in significant ways, by the neo-conservative and neo-nationalist movements that grew to political significance in the 1980s and 1990s.”

Citation: Andrew Jamison, Climate change knowledge and social movement theory, Wiley Interdisciplinary Reviews: Climate Change, Volume 1, Issue 6, pages 811–823, November/December 2010, DOI: 10.1002/wcc.88. [abstract, full text]

Sulfur hexafluoride concentration is increasing

Sulfur hexafluoride is the strongest greenhouse gas with global warming potential of 22,800. It’s current concentration is low so it contributes only 0.1 % of total anthropogenic radiative forcing. Rigby et al. have analysed atmospheric measurements of sulfur hexafluoride and published a record of sulfur hexafluoride concentration between 1973 and 2008. The concentration is on the rise:

“Atmospheric mole fractions were found to have increased by more than an order of magnitude between 1973 and 2008. The 2008 growth rate was the highest recorded, at 0.29 ± 0.02 pmolmol−1 yr−1.”

They also studied the emissions:

“Consistent with the mole fraction growth rate maximum, global emissions during 2008 were also the highest in the 1973–2008 period, reaching 7.4 ± 0.6 Gg yr−1 (1-σ uncertainties) and surpassing the previous maximum in 1995.”

They note that between 2004 and 2008:

“…we find that it is likely that much of the global emissions rise during this five-year period originated primarily from Asian developing countries that do not report detailed, annual emissions to the United Nations Framework Convention on Climate Change (UNFCCC).”

Citation: Rigby, M., Mühle, J., Miller, B. R., Prinn, R. G., Krummel, P. B., Steele, L. P., Fraser, P. J., Salameh, P. K., Harth, C. M., Weiss, R. F., Greally, B. R., O’Doherty, S., Simmonds, P. G., Vollmer, M. K., Reimann, S., Kim, J., Kim, K.-R., Wang, H. J., Olivier, J. G. J., Dlugokencky, E. J., Dutton, G. S., Hall, B. D., and Elkins, J. W.: History of atmospheric SF6 from 1973 to 2008, Atmos. Chem. Phys., 10, 10305-10320, doi:10.5194/acp-10-10305-2010, 2010. [abstract, full text]

No sign of MWP in East Antarctic coast

Holocene geological records from East Antarctic coast have been reviewed in a new study. Two warm periods are found. The Early Holocene warm period (11.5-9 ka BP) shows in records very clearly and synchronously. Quite well shows also another warm period between 4.7 and 1 ka BP but for this one there’s little more timing differences between the records. On the MWP and LIA:

“There is no evidence along the East Antarctic coastline for an equivalent to the Northern Hemisphere Medieval Warm Period and there is only weak circumstantial evidence in a few places for a cool event crudely equivalent in time to the Northern Hemisphere’s Little Ice Age.”

Citation: Verleyen, E., et al. (2010), Post-glacial regional climate variability along the East Antarctic coastal margin – evidence from shallow marine and coastal terrestrial records, Earth-Science Reviews, doi:10.1016/j.earscirev.2010.10.006. [abstract]

Tropical ozone doesn’t recover to pre-1980’s values

New study has looked how the ozone situation evolves in the future by using climate model simulations. Result for the tropics is:

“In the tropics, simulated peak ozone amounts occur by about 2050 and thereafter total ozone column declines. Consequently, simulated ozone does not recover to values which existed prior to the early 1980s.”

In the northern and southern hemisphere situation differs from each other:

“The results also show a distinct hemispheric asymmetry, with recovery to 1980 values in the Northern Hemisphere extratropics ahead of the chlorine return by about 20 years. In the Southern Hemisphere midlatitudes, ozone is simulated to return to 1980 levels only 10 years ahead of chlorine. In the Antarctic, annually averaged ozone recovers at about the same rate as chlorine in high latitudes and hence does not return to 1960s values until the last decade of the simulations.”

Citation: Austin, J., et al. (2010), Decline and recovery of total column ozone using a multimodel time series analysis, J. Geophys. Res., 115, D00M10, doi:10.1029/2010JD013857. [abstract]

Cyclones change location with global warming

Li et al. have studied how cyclone frequency evolves in North Pacific while the globe is warming. They used climate models with A1B scenario. They found a change in cyclones:

“A significant shift is found in the location of tropical cyclones from the western to central Pacific. The shift to more tropical cyclones in the central and less in the western Pacific is not attributable to a change in atmospheric static stability, but to a change in the variance of tropical synoptic-scale perturbations associated with a change in the background vertical wind shear and boundary layer divergence.”

Citation: Li, T., M. Kwon, M. Zhao, J.-S. Kug, J.-J. Luo, and W. Yu (2010), Global warming shifts Pacific tropical cyclone location, Geophys. Res. Lett., 37, L21804, doi:10.1029/2010GL045124. [abstract, full text]

Contribution of sea ice loss to Arctic amplification

In a new study the observed sea ice conditions during 2007 were fed to climate models in an effort to gain further information of how sea ice contributes to the Arctic amplification of global warming. It turns out that sea ice loss causes almost all of the amplification. The effect of the sea ice to the amplification only contributes in the high latitudes (north from 60°N) both in surface and in atmosphere. The amplification induced warming occurs vertically within lowest 1000 meters. The temperature response to sea ice loss is strongly seasonal:

“A weak signal of Arctic amplification in surface based warming is found during boreal summer, whereas a dramatically stronger signal is shown to develop during early autumn that persisted through December even as sea ice coverage approached its climatological values in response to the polar night.”

Citation: Kumar, A., J. Perlwitz, J. Eischeid, X. Quan, T. Xu, T. Zhang, M. Hoerling, B. Jha, and W. Wang (2010), Contribution of sea ice loss to Arctic amplification, Geophys. Res. Lett., 37, L21701, doi:10.1029/2010GL045022. [abstract, full text]


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