Note: this is a blog I created whilst following a MOOC on Climate Change
We were asked to reflect on three key questions:
1. What [are] the key scientific principles that explain climate change including the greenhouse (blanket) effect?
The earth maintains a temperature (on average 15C) that is comfortable to life. The incoming radiation from the sun is balanced by outgoing radiation from the earth – either directly reflecting the incoming radiation, or absorbing it and re-emitting it at longer wavelengths. Gases in the atmosphere, including water vapour, carbon dioxide, methane, ozone and nitrous oxide, can be considered as forming a ‘blanket’ which retains heat: temperatures would be much lower without them. However, if the amount of greenhouse gases in the atmosphere increases, more heat is retained, warming the earth.
2. What are the key feedback mechanisms that help to explain why our climate is able to “self-regulate”?
Positive Feedbacks: water vapour, ice albedo. If the earth starts to warm, both of these will act to make it warmer. Likewise, if it starts to cool, these will act to cool it further.
Negative Feedback: radiation. If the earth warms, heat radiation will increase and act to cool it.
3. How can our climate be conceptualised as a system containing a series of components that interact with one another?
How can it not be? The alternative is a bunch of angry gods, which is not a helpful model. Components identified so far are the atmosphere, hydrosphere, biosphere, cryosphere and lithosphere. These are connected by various cycles, of which we have learned about the water cycle, and these cycles incorporate feedback loops, some positive, some negative (see 2 above). More to come in week 2, I hope.
For me, the most important thing this week was seeing the figures and diagram for earth’s energy balance of incoming and outgoing radiation. I was particularly struck by the size of the back radiation, and this is clearly a key point.
I also learned that I hadn’t known how a greenhouse really worked, which is why the ‘greenhouse effect’ had always seemed a reasonable name to me. Hmm…