Possumblog

The history channel or one like it had a program on the little ice age [app. 1300-1830]. You could tell they hated not being able to blame bush or the United States.

Great post, I LOLed at the thought of a Bush/Rove Time Machine.

I recommend reading what the authors are actually saying about their own study. The study connects past warming to natural variations in Earth's orbit—obliquity, or how tilted the planet is in relation to the sun. Author Martin Sharp points out "One could argue that this shows that natural forcing could account for the current warm conditions, but the current orbital configuration does not support this, even when other natural forcings are taken into account." In other words, their study "really has nothing to say about the mechanisms driving the current warming."

They discovered the Greenland ice shelf is at least 400,00 to 800,000 years old. Certainly it was around the time Erik the Red named the island. According to author Eske Willerslev, the Greenland ice shelf "has not contributed to global sea level rise during the last interglacial. Importantly, it does not mean that we should not be worried about future global warming as the sea level rise of five to six meters during the last interglacial must have come from somewhere."

Finally, Martin Sharp warns the study "does not prove the current global warming trend is not human induced". If anything, "we may be heading for even bigger temperature increases than we previously thought".

Thank you, John--despite my constant derision directed at people like Al Gore, I'm actually not convinced that there is no anthropogenic basis for potential changes in the climate. We really could be having an effect, but the magnitude of that effect is still something I'm not willing to place bets on.

I'd just like folks to be a bit more circumspect about it, and realize that there are all sorts of variables involved that might play a much, much larger role in variations in global temperatures.

The current politically driven pseudoreligio-hysteriecofad isn't serving anyone very well, nor is the desire to constantly attempt to blame everything bad on global warming.

Hi Terry, thanks for the reply,

I subscribe to anthropogenic global warming and even I'm annoyed by some of the more hysterical rantings by environmentalists. It's been my observation that an averion to alarmism is one of the big factors in global warming skepticism so hysteria only exacerbates that. But that's the way it is - the hysterical voices are the loudest and get the most attention.

Nevertheless, underneath that is serious, meticulous science which is why I always try and read what the scientists say (eg - with the Greenland study). I also find the scientists very approachable - if I ever have any questions and email the authors of a particular study directly, they've always replied very quickly and helpfully. And it's my impression that at the scientific level, they are being circumspect.

Scientists have known for a long time now that CO2 is the primary driver of the last 30 years of global warming but due to the uncertainties of climate science, have always calculated their results with large error bars. However, as more data comes in and the climate models improve, the uncertainty diminishes. In 2001, projected temperature rises by 2100 were between 1.4°C to 5.8°C - in 2007, this has narrowed to 2°C to 4.5°C as the science improves.

And the IPCC have failed to include positive feedback systems in their modelling due to lack of certainty in how they act. Eg - as ice caps melt, Earth's albedo (reflectivity) reduces which accelerates warming. As permafrost thaws, it emits methane - another greenhouse gas. These feedback systems are not factored in so while there is uncertainty in climate predictions, they could be underestimating rather than overestimating future temperature rise.

If everyone would take your approach to discussing the topic, John, it would be a lot more constructive and useful. Unfortunately, there are quite a few too many people who see a witch at every turn.