Originally posted at Skeptical Science
The previous article in this series looked at the recent discovery of significant releases of fossil methane through the thawing permafrost in Alaska. In this second instalment we will look at the potential of the rest of the Arctic to produce subcap methane, and will compare the size of these seeps to other global methane-producing mechanisms.
Originally posted at Skeptical Science
The previous two parts (one here and two here) of this series examined the evidence for seeps of geological methane through the cap provided by permafrost and looked at estimates of the magnitude of such seeps in relation to other sources of atmospheric methane. In this section, we will look at the emerging evidence for actual and potential methane releases related to glaciers and ice sheets. The sources of this methane are varied: fossil methane released through reactivated fractures; organic matter once buried and now exhumed; and possible methane hydrates lurking under the big ice sheets.
Originally posted at Skeptical Science
Previous articles in this series have reviewed recent research on methane sources from beneath permafrost and ice sheets. Part 1 looked at subcap fossil methane seeps in Alaska;Part 2 provided a perspective for the size of these seeps in relation to other natural and human sources; and Part 3 looked at potential methane sources resulting from the withdrawal of glaciers and ice sheet. In this final section, I will try to make estimates of what subcap methane emissions may mean for future climate change; more as a speculative basis for discussion rather than an authoritative prediction. Firstly, though, I will argue for a role for subcap methane emissions on the East Siberian Arctic Shelf (ESAS).
Originally posted at Skeptical Science and reposted at Climate Progress.
A recent modelling experiment shows that climate change feedbacks from thawing permafrost are likely to increase global temperatures by one-quarter to a full degree Celsius by the end of this century. This extra warming will be in addition to the increase in temperature caused directly by emissions from fossil fuels. Even in the unlikely event that we were to stop all emissions in the near future, this permafrost climate feedback would likely continue as a self-sustaining process, cancelling out any future natural draw-down in atmospheric carbon dioxide levels by the oceans or vegetation. Avoiding dangerous climate change by reducing fossil-fuel emissions becomes more difficult once permafrost emissions are properly considered.
Originally posted at Skeptical Science
Originally posted at Skeptical Science
Sudden spikes in global temperatures that occurred 50-55 million years ago were caused by thawing of permafrost in Antarctica and northern high latitudes, according to recent research. The trigger for this sudden destabilization was a variation in orbital configurations that resulted in warmer polar summers. This model also provides an analogue for the releases of carbon from modern permafrost caused by current man-made global warming. Modern permafrost volumes are smaller than the estimates for those of 55 million years ago, but will nevertheless amplify the climatic effect of fossil fuel consumption and will provide continuing warming feedbacks for centuries after human emissions cease. Continue reading
Originally posted at Skeptical Science
Fifty million years ago, during the Eocene Epoch , the world had a very different climate, with temperatures much higher than today’s, especially at the poles. This hothouse climate was caused mainly by CO2 levels that were twice as high, or more, than now. On our current emissions trajectory, we could recreate the chemistry of the hothouse atmosphere before the end of this century, with potentially drastic consequences for our climate.
Originally posted on 21 October 2011 at Skeptical Science
A paper submitted for peer review by the Berkeley Earth Surface Temperature study (BEST)finds that urban heating has an influence on global temperature trends that is “nearly negligible” and that what effect has been observed is even slightly negative, which is to say that temperature trends in urban areas are actually cooler than the trends measured at rural sites, and that the Earth’s land surface has warmed approximately 1°C on average since 1950.
It has long been observed that temperatures in cities are higher than in the surrounding countryside, caused, in part, by human structures that reduce albedo and evapo-transpiration, as well as by the effects of waste heat emissions, McCarthy et al 2010. Even though most (99%) of the Earth’s surface is not urbanized, some 27% of the Monthly Global Historical Climatology Network (GHCN-M) temperature stations are located in cities having populations of more than 50,000. Since urbanization has grown dramatically over the past few centuries, it seems reasonable to ask how much of the observed rise in global temperatures is due to urbanization. For example, McKitrick and Michaels claimed in 2007 that about half of the recent warming over land is due to urban heat island effect, although this result was disputed bySchmidt in 2009.
Several studies have looked in depth at possible heat island contamination of land temperature records. For example, Hansen et al in 2010 used satellite measurements of night lights to remove possibly affected urban sites from the temperature records. Allowing for urban effects reduced the global temperature trend over the period 1900-2009 by 0.01°C. Menne et alperformed an analysis on US surface temperature records and found only very small effects due to poor siting of temperature stations. They reported that poorly-sited stations did show some small positive bias in recorded minimum temperatures but there was a small, but slightly larger, negative bias in recorded maximum temperatures, resulting in an overall small residual cool bias.
Originally posted at Skeptical Science on 30 July 2011
This is a three-part series on science writer, businessman and climate contrarian Matt Ridley. The first section looks at his science books and is critical of his latest book, The Rational Optimist; the second scrutinizes one of his blog posts on climate change and shows that his avowed lukewarmer stance is built on shaky scientific foundations; the final part examines Ridley’s history as a businessman, drawing parallels between his role in the credit crunch and his approach to climate change.
Sometimes, it’s easy to dismiss climate change contrarians as being a little slow when it comes to truly understanding science, but it’s not possible to do that with Matt Ridley, who has a well-earned reputation as a first-class science writer. He is on the Academic Advisory Council of the contrarian Global Warming Policy Foundation, along with Robert Carter, William Happer, Richard Lindzen, and Ian Plimer. As well as being the author of several excellent science books, he’s a journalist, a businessman, and has a D.Phil. in Zoology from Oxford. And he runs a blog that, among other things, takes a skeptical stance on the mainstream science of climate change.
Why such a talented science writer should have come to reject the scientific consensus on climate change is the Ridley Riddle that this series of posts will attempt to answer.
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