Mr. Scientist

I often use this blog as a repository for links. Rather than writing my opinions on a particular subject, I would rather link to what the various scientists have to say. It allows for quick access to the primary sources, and allows me to archive information sources that I find useful in a way that allows me to easily retrieve them.

Recently, a friend (Steven Morello) wrote to me, and asked me to put up a detailed summary he had written on various areas of climate science. I have been meaning to do so for a while, but alas, I have been short on time. I’ll endeavour to put up his summary, piece by piece, over the next few weeks. It is very good, and somewhat complimentary to most the pieces I have put up on this blog. Anyway, here is the first section of his summary – enjoy!

Climate change in the past was natural, but adding extra human forcing is changing the earth’s planetary energy balance

Climate has changed in the past. Sometimes it changes quite dramatically. Why? When something causes a change in global temperature, such as varying solar activity or changes in the Earth’s orbit, feedbacks amplify these changes. The atmosphere grows more humid, and, as water vapour is a greenhouse gas, this traps more heat. Arctic sea ice melts, causing the exposed ocean to absorb more heat. The feedbacks aren’t so large that they lead to runaway warming but they are enough to amplify one degree of greenhouse warming to three degrees of total warming. Many different periods throughout Earth’s history, from the last few millennia to millions of years ago, yield remarkably consistent results establishing this amount of climate feedback.

When geologists bring up past climate change, they’re actually citing evidence for climate feedback. Dramatic swings in global temperature, dragging the planet in and out of ice ages, are possible because of these feedbacks. Renowned paleoclimatologist Wally Broecker sums it up beautifully: “The paleoclimate record shouts out to us that, far from being self-stabilising, the Earth’s climate system is an ornery beast which overreacts to even small nudges.”

We have already given our climate a big nudge. How do we know it’s us causing the warming and not natural causes? Because we’ve directly measured it. Satellites measure reductions in heat escaping to space – direct empirical evidence that carbon emissions are trapping heat. Surface measurements measure more heat returning to Earth, confirming the increased greenhouse effect. We see many signatures of greenhouse warming such as winters warming faster than summers, cooling upper atmosphere with warming lower atmosphere and nights warming faster than days. The case for human-caused warming is based on many independent lines of evidence.

The feedbacks that amplified past climate change are now amplifying the warming caused by our carbon emissions. We’re measuring more water vapour in the atmosphere, a strong feedback. Arctic sea ice is disappearing and satellites measure less sunlight reflected back to space – another significant feedback. The Earth’s past and modern measurements all paint a consistent picture – our climate is already overreacting to our “nudge”.

http://www.abc.net.au/environment/articles/2011/06/08/3226946.htm