Paul

Biological productivity controls cloud formation and may be the lever that caused supergreenhouse episodes during the Cretaceous and Eocene, according to Penn State paleoclimatologists.

“Our motivation was the inability of climate models to reproduce the climate of the supergreenhouse episodes of the Cretaceous and Eocene adequately,” said Lee R. Kump, professor of geosciences. “People have tried increasing carbon dioxide in the models to explain the warming, but there are limits to the amounts that can be added because the existing proxies for carbon dioxide do not show such large amounts.”

In general, the proxies indicate that the Cretaceous and Eocene atmosphere never exceeded four times the current carbon dioxide level, which is not enough for the models to create supergreenhouse conditions. Some researchers have tried increasing the amount of methane, another greenhouse gas, but there are no proxies for methane. Another approach is to assume that ocean currents changed, but while researchers can insert new current information into the models, they cannot get the models to create these ocean current scenarios.

Kump and David Pollard, senior research associate, Earth and Environmental Systems Institute, looked for another way to create a world where mean annual temperatures in the tropics were above 100 degrees Fahrenheit and polar temperatures were in the 50-degree Fahrenheit range. Changing the Earth’s albedo — the amount of sunlight reflected into space – by changing cloud cover will produce supergreenhouse events, the researchers report in today’s (April 11) issue of Science.

“The model reduces cloud cover from about 64 percent to 55 percent which lets in a large amount of direct sunlight,” Kump says. “The increased breaks in the clouds, fewer clouds and less reflective clouds produced the amount of warming we were looking for.”

EurekAlert: Absence of clouds caused pre-human supergreenhouse periods

National Geographic: Lack of Clouds Amplified Dino-Era Warming, Study Says

Abstract:

Amplification of Cretaceous Warmth by Biological Cloud Feedbacks

Lee R. Kump1* and David Pollard2

The extreme warmth of particular intervals of geologic history cannot be simulated with climate models, which are constrained by the geologic proxy record to relatively modest increases in atmospheric carbon dioxide levels. Recent recognition that biological productivity controls the abundance of cloud condensation nuclei (CCN) in the unpolluted atmosphere provides a solution to this problem. Our climate simulations show that reduced biological productivity (low CCN abundance) provides a substantial amplification of CO2-induced warming by reducing cloud lifetimes and reflectivity. If the stress of elevated temperatures did indeed suppress marine and terrestrial ecosystems during these times, this long-standing climate enigma may be solved.

1 Department of Geosciences and Earth System Science Center, Pennsylvania State University, University Park, PA 16802, USA.
2 Earth and Environmental Systems Institute, Pennsylvania State University, University Park, PA 16802, USA.

The April edition of Birmingham University’s newsletter BUZZ incudes comment from climate researcher Chris Kidd that,

“Despite these warmer temperatures and recent news of further ice-shelf melting, global temperatures do appear to be cooling after reaching a peak in 1998.

Since then the temperatures steadied and have fallen over the past couple of years: in fact, Antarctica saw its greatest recorded extent of ice in 2007, unlike the dwindling Arctic sea ice.

As for the summer, seasonal forecasting is best left to computer models to get wrong, but it would seem that we could be in for an ‘average’ summer: cool and showery.”

Let’s hope Jo Abbess, the activist who recently insisted the BBC change a story that mentioned some global cooling, doesn’t try and get this article changed!

———————–
Dr Chris Kidd is from the Climate and Atmospheric Research Group, in the School of Geography, Earth and Environmental Sciences, University of Birmingham, and he is not a climate skeptic.

At the time of writing the April Edition was not yet available online.

This Story was edited by Jennifer at 9.30am on April 10.

On Thursday 3rd April BBC News website’s Richard Black penned an article entitled, ‘No Sun link’ to climate change, based on a flawed paper (not discussed in detail here) in a lesser known journal called Environmental Research Letters, which refers only to Palle/Butler and Marsh/Svensmark (2000), but not Shaviv/Veizer.

The article begins:

Scientists have produced further compelling evidence showing that modern-day climate change is not caused by changes in the Sun’s activity.

The research contradicts a favoured theory of climate “sceptics”, that changes in cosmic rays coming to Earth determine cloudiness and temperature.

The idea is that variations in solar activity affect cosmic ray intensity.

But Lancaster University scientists found there has been no significant link between them in the last 20 years.

The paper referred to is: ‘Testing the proposed causal link between cosmic rays and cloud cover’

The paper concludes:

In conclusion, no corroboration of the claim of a causal connection between the changes in ionization and low cloud
cover, made in [1, 2], could be found in this investigation. From the distribution of the depth of the dip in solar cycle 22 with geomagnetic latitude (the VRCO) we find that, averaged over the whole Earth, less than 23% of the dip comes from the solar modulation of the cosmic ray intensity, at the 95% confidence level. This implies that, if the dip represents a real correlation, more than 77% of it is caused by a source other than ionization and this source must be correlated with solar activity.

Not exactly, ‘no link.’ and Giles Harrison from Reading University, is quoted as saying that the work was important “as it provides an upper limit on the cosmic ray-cloud effect in global satellite cloud data”.

Harrison’s own UK study from 2006 concluded,

Changes in diffuse fraction (DF) and the frequency of overcast days represent changes in the weather and the atmospheric energy balance. The decrease in the proportion of direct solar radiation associated with an increase in DF will lead to a local reduction in daytime surface temperature. Further, because the net global effect of cloud is cooling (Hartman 1993), any widespread increase in the overcast days could also reduce temperature. At Reading, the measured sensitivity of daily average temperatures to DF for overcast days is K0.2 K per 0.01 change in DF for 1997–2004). Consequently the inverse relationship between GCR and solar activity will lead to cooling at solar minimum. This might amplify the effect of the small solar cycle variation in total solar irradiance, believed to be underestimated by climate models (Stott et al. 2003), which neglect a cosmic ray effect. In summary, our data analysis confirms the existence of a small, yet statistically robust, cosmic ray effect on clouds, that will emerge on long time scales with less variability than the considerable variability of daily cloudiness.

No mention is made by the BBC of the more favourable 2008 review of the evidence for a cosmic ray-climate link by Usoskin and Kovaltsov, which concluded: “a CR-climate link seems to be a plausible climate driver, as supported by the bulk of statistical studies and existing theoretical models. However, further studies, in particular a clear case study as well as improved model development, are foreseen to improve our understanding of the link between cosmic rays and the climate on Earth.”

NOW YOU SEE IT, NOW YOU DON’T!

Moving on to the strange happenings surrounding a subsequent 4th April article by the BBC’s Roger Harrabin, blogged here, entitled, Global temperatures ‘to decrease’ , which was later changed to, Global warming ‘dips this year, ‘ and then subsequently changed back to Global temperatures ‘to decrease.’ The changes in the text, however, did not revert back to the text in the original article.

The two alternative headings an be viewed on this google search:

http://www.google.co.uk/search?sourceid=navclient&ie=UTF-8&rlz=1T4ADBR_enGB245GB248&q=Global+warming+to+dip+this+year

Referring to the forecast a record high temperature within five years, “probably associated with another episode of El Nino” was permanently removed from the re-written article. If the Freedom of Information Act is applicable to the BBC, I shall make a request in order to try and uncover the sequence of events and the reasons behind them.

See also NewsBusters: BBC Changes ‘Temperatures Decrease’ Article to Incite Climate Hysteria

The Committee on Climate Change is being created as a new expert body, to provide independent advice to the UK Government and Devolved Administrations on how the UK can optimally achieve its emissions reductions goals for 2020 and 2050.

Opportunity details:

Board Committee Committee on Climate Change £800 per day