The Geological Society released a Statement on the climate this week. (http://www.geolsoc.org.uk/gsl/views/policy_statements/climatechange). It is based on geological evidence only and does not include any climate model projections or recent temperature or satelite data.
In the final sentances it concludes that if we continue business as usual and reach an emissions level of 1500 to 2000 billion tonnes of carbon (currently we have emitted 500 billion tonnes since we started clearing land for agriculture) then…
“recovery of the Earth’s climate in the absence of any mitigation measures could take 100,000 years or more”
This is a considerable increase in the estimated time to recover the climate, which was previously stated as 1000 years. We are currently poised to reach a total emission of 1000 billion tonnes within the next few decades. If this releases methane stored in the tundra and in the shallow seas north of Siberia, we could easily reach 2000 bt this century.
The Statement also provides a roundup of the geological basis for climate changes in the past and the geological evidence for human influence in the changes seen over the last 250 years. They give the answer to the question of when was the CO2 concentration similar to today’s:
“The most recent estimates suggest that at times between 5.2 and 2.6 million years ago (during the Pliocene), the carbon dioxide concentrations in the atmosphere reached between 330 and 400 ppm [ed. now 390 ppm]. During those periods, global temperatures were 2-3°C higher than now, and sea levels were higher than now by 10 – 25 metres, implying that global ice volume was much less than today”
This suggests that the IPCC projections are woefully inadequate. We have already set in train very serious changes in ice volume and could expect a sea level rise of 10s of meters within the next couple of hundred years.
We call again on our politicians to take firm and ambitious action to replace our fossil fuel systems with renewable energy. The technology is all there. All we need is the leadership to get this done.