AGW Observer

Observations of anthropogenic global warming

New research from last week 3/2011

Posted by Ari Jokimäki on January 24, 2011

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 they are published. 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. Here’s the archive for the news of previous weeks. 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:

Reconstructing climate forcing of 1000 years

Climate forcing reconstructions for use in PMIP simulations of the last millennium (v1.0) – Schmidt et al. (2011) “Simulations of climate over the Last Millennium (850–1850 CE) have been incorporated into the third phase of the Paleoclimate Modelling Intercomparison Project (PMIP3). The drivers of climate over this period are chiefly orbital, solar, volcanic, changes in land use/land cover and some variation in greenhouse gas levels. While some of these effects can be easily defined, the reconstructions of solar, volcanic and land use-related forcing are more uncertain. We describe here the approach taken in defining the scenarios used in PMIP3, document the forcing reconstructions and discuss likely implications.” Schmidt, G. A., Jungclaus, J. H., Ammann, C. M., Bard, E., Braconnot, P., Crowley, T. J., Delaygue, G., Joos, F., Krivova, N. A., Muscheler, R., Otto-Bliesner, B. L., Pongratz, J., Shindell, D. T., Solanki, S. K., Steinhilber, F., and Vieira, L. E. A., Geosci. Model Dev., 4, 33-45, doi:10.5194/gmd-4-33-2011, 2011. [full text]

Historic events of mankind don’t show in ice core CO2

Coupled climate–carbon simulations indicate minor global effects of wars and epidemics on atmospheric CO2 between AD 800 and 1850 – Pongratz et al. (2011) “Historic events such as wars and epidemics have been suggested as explanation for decreases in atmospheric CO2 reconstructed from ice cores because of their potential to take up carbon in forests regrowing on abandoned agricultural land. Here, we use a coupled climate–carbon cycle model to assess the carbon and climate effects of the Mongol invasion (∼1200 to ∼1380), the Black Death (∼1347 to ∼1400), the conquest of the Americas (∼1519 to ∼1700), and the fall of the Ming Dynasty (∼1600 to ∼1650). We calculate their impact on atmospheric CO2 including the response of the global land and ocean carbon pools. It has been hypothesized that these events have contributed to significant increases in land carbon stocks. However, we find that slow regrowth and delayed emissions from past land cover change allow for small increases of the land biosphere carbon storage only during long-lasting events. The effect of these small increases in land biosphere storage on global CO2 is reduced by the response of the global carbon pools and largely offset by concurrent emissions from the rest of the world. None of these events would therefore have affected the atmospheric CO2 concentration by more than 1 ppm. Only the Mongol invasion could have lowered global CO2, but by an amount too small to be resolved by ice cores.” Julia Pongratz, Ken Caldeira, Christian H. Reick, Martin Claussen, The Holocene January 20, 2011 0959683610386981, doi: 10.1177/0959683610386981.

Climate related soil temperature trends in Canada

Observed soil temperature trends associated with climate change in Canada – Qian et al. (2011) “Trends in soil temperature are important, but rarely reported, indicators of climate change. On the basis of the soil temperature data from 30 climate stations across Canada during 1958–2008, trends in soil temperatures at 5, 10, 20, 50, 100, and 150 cm depths were analyzed, together with atmospheric variables, such as air temperature, precipitation, and depth of snow on the ground, observed at the same locations. There was a significant positive trend with soil temperatures in spring and summer means, but not for the winter and annual means. A positive trend with time in soil temperature was detected at about two-thirds of the stations at all depths below 5 cm. A warming trend of 0.26–0.30°C/decade was consistently detected in spring (March–April–May) at all depths between 1958 and 2008. The warming trend in soil temperatures was associated with trends in air temperatures and snow cover depth over the same period. A significant decreasing trend in snow cover depth in winter and spring was associated with increasing air temperatures. The combined effects of the higher air temperature and reduced snow depth probably resulted in an enhanced increasing trend in spring soil temperatures, but no significant trends in winter soil temperatures. The thermal insulation by snow cover appeared to play an important role in the response of soil temperatures to climate change and must be accounted for in projecting future soil-related impacts of climate change.” Qian, B., E. G. Gregorich, S. Gameda, D. W. Hopkins, and X. L. Wang (2011), J. Geophys. Res., 116, D02106, doi:10.1029/2010JD015012.

2010 record melting in Greenland

The role of albedo and accumulation in the 2010 melting record in Greenland – Tedesco et al. (2011) “Analyses of remote sensing data, surface observations and output from a regional atmosphere model point to new records in 2010 for surface melt and albedo, runoff, the number of days when bare ice is exposed and surface mass balance of the Greenland ice sheet, especially over its west and southwest regions. Early melt onset in spring, triggered by above-normal near-surface air temperatures, contributed to accelerated snowpack metamorphism and premature bare ice exposure, rapidly reducing the surface albedo. Warm conditions persisted through summer, with the positive albedo feedback mechanism being a major contributor to large negative surface mass balance anomalies. Summer snowfall was below average. This helped to maintain low albedo through the 2010 melting season, which also lasted longer than usual.” M Tedesco, X Fettweis, M R van den Broeke, R S W van de Wal, C J P P Smeets, W J van de Berg, M C Serreze and J E Box, Environmental Research Letters, Volume 6, Number 1, doi: 10.1088/1748-9326/6/1/014005.

Did atomic bombs cause 1940′s cooling?

The Role of Atmospheric Nuclear Explosions on the Stagnation of Global Warming in the Mid 20th Century – Fujii (2011) “This study suggests that the cause of the stagnation in global warming in the mid 20th century was the atmospheric nuclear explosions detonated between 1945 and 1980. The estimated GST drop due to fine dust from the actual atmospheric nuclear explosions based on the published simulation results by other researchers (a single column model and Atmosphere-Ocean General Circulation Model) has served to explain the stagnation in global warming. Atmospheric nuclear explosions can be regarded as full-scale in situ tests for nuclear winter. The non-negligible amount of GST drop from the actual atmospheric explosions suggests that nuclear winter is not just a theory but has actually occurred, albeit on a small scale. The accuracy of the simulations of GST by IPCC would also be improved significantly by introducing the influence of fine dust from the actual atmospheric nuclear explosions into their climate models; thus, global warming behavior could be more accurately predicted.” Yoshiaki Fujii, Journal of Atmospheric and Solar-Terrestrial Physics, 2011, doi:10.1016/j.jastp.2011.01.005.

Increasing frequencies of heat waves attributable to human influence

Single-step attribution of increasing frequencies of very warm regional temperatures to human influence – Stott et al. (2011) “Seasonal near-surface temperatures have increased in many regions of the World. Previous work has shown that this has led to rapidly increasing frequencies of very warm Northern Hemisphere summer temperatures. Here we show, using a ‘single-step’ attribution framework, that increases in frequencies of very warm seasonal temperatures, not just in Northern Hemisphere summers but in other regions and seasons, can be directly attributed to human influence. In the June-August and September-November seasons, many of the sub-continental regions of Africa and Asia show robust attributable increase in the frequencies of anomalously warm seasonal temperatures.” Peter A. Stott, Gareth S. Jones, Nikolaos Christidis, Francis W. Zwiers, Gabriele Hegerl, Hideo Shiogama, Atmospheric Science Letters, DOI: 10.1002/asl.315.

NH cryosphere albedo feedback is larger than models predict

Radiative forcing and albedo feedback from the Northern Hemisphere cryosphere between 1979 and 2008 – Flanner et al. (2011) “The extent of snow cover1 and sea ice2 in the Northern Hemispherehas declined since 1979, coincident with hemispheric warming and indicative of a positive feedback of surface reflectivity on climate. This albedo feedback of snow on land has been quantified from observations at seasonal timescales3, 4, 5, 6, and century-scale feedback has been assessed using climate models7, 8, 9, 10. However, the total impact of the cryosphere on radiative forcing and albedo feedback has yet to be determined from measurements. Here we assess the influence of the Northern Hemisphere cryosphere on Earth’s radiation budget at the top of the atmosphere—termed cryosphere radiative forcing—by synthesizing a variety of remote sensing and field measurements. We estimate mean Northern Hemisphere forcing at −4.6 to −2.2 W m−2, with a peak in May of −9.0±2.7 W m−2. We find that cyrospheric cooling declined by 0.45 W m−2 from 1979 to 2008, with nearly equal contributions from changes in land snow cover and sea ice. On the basis of these observations, we conclude that the albedo feedback from the Northern Hemisphere cryosphere falls between 0.3 and 1.1 W m−2 K−1, substantially larger than comparable estimates obtained from 18 climate models.” M. G. Flanner, K. M. Shell, M. Barlage, D. K. Perovich & M. A. Tschudi, Nature Geoscience, 2011, DOI: doi:10.1038/ngeo1062.

GHG warming detected in Europe since 17th century

Influence of human and natural forcing on European seasonal temperatures – Hegerl et al. (2011) “It is the regional and seasonal expression of climate change that determines the effect of greenhouse warming on ecosystemsand society. Whereas anthropogenic influences on European temperatures have been detected over the twentieth century, it has been suggested that the impact of external influences on European temperatures before 1900 is negligible. Here we use reconstructions of seasonal European land temperature5, 6 and simulations with three global climate models to show that external influences on climate—such as the concentrations of stratospheric volcanic aerosols or greenhouse gases, other anthropogenic effects and possibly changes in total solar irradiance—have had a discernible influence on European temperatures throughout the past five centuries. In particular, we find that external forcing contributes significantly (p<5%) to the reconstructed long-term variability of winter and spring temperatures and that it is responsible for a best guess of 75% of the observed winter warming since the late seventeenth century. This warming is largely attributable to greenhouse-gas forcing. Summer temperatures show detectable (p<5%) interdecadal variations in response to external forcing before 1900 only. Finally, throughout the record we detect highly significant summer cooling and significant winter warming following volcanic eruptions." Gabriele Hegerl, Juerg Luterbacher, Fidel González-Rouco, Simon F. B. Tett, Thomas Crowley & Elena Xoplaki, Nature Geoscience, 2011, DOI: doi:10.1038/ngeo1057.

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3 Responses to “New research from last week 3/2011”

  1. [...] was going to blog about some of these papers, but then decided I’d simply send you guys there [...]

  2. Kit Stolz said

    The “nuclear winter” theory to explain the cooling of the 40′s is interesting. Do you have any ideas on how to find out what the reaction in the field has been to this suggestion? Thanks…

  3. Ari Jokimäki said

    My ideas on that are quite standard: trying to find something with web searches, asking scientists, or waiting for the peer-reviewed response (possibly in few months). :)

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