These are notes from the last talk of the MAA North Central Section-sponsored summer seminar on conceptual climate models. This talk by Anna Barry tied together all the things we'd learned about over the past two days in discussing the snowball earth hypothesis, which tries to explain some mysterious pieces of paleoclimate evidence, and whether or not there is a mathematical basis for the idea.
So, let's get started!
What could initiate a snowball earth state?
Ice-albedo feedback, which we discussed earlier (more ice -> higher albedo (more reflectivity) -> less energy in, as more solar energy is reflected -> colder -> more ice).
More notes from the MAA-sponsored North Central Section summer seminar on conceptual climate models. This is from Richard McGehee's talk on understanding the climate of the past and the Milankovitch cycles. These notes give some overview, but the graphs are really important to understanding these ideas and I will work on finding some to include.
Some thought-provoking questions: If we can’t even predict the weather, how can we predict the future? If we don’t know about the climates of the past, how can we expect to predict the future? The question is somewhat controversial: some climate modelers feel we only need to understand today and then we can play it all forward using big general climate models.
How do we know the climates of the past?
Lake Vostok, Antarctica. 2.2 miles of ice on top of a tiny little pool of water down near the earth. Scientists have taken core samples from here and “gone back in time.” “Isotopes in the ice are proxies for past atmospheric temperatures above the Antarctic”: Continue reading
Jim Walsh from Oberlin opened today by talking about greenhouse gases and energy balance equations. His slides are online -- check them out for all the great pictures I have not included!
First big conceptual point: global climate is determined by the energy in minus the energy out. Since energy in is basically the insolation ( -- incoming solar radiation) that is not reflected (multiply by 1-albedo) and energy out is OLR (outgoing longwave radiation) these are the three factors to look at -- change in insolation, albedo, or OLR. If these are changed by our human activities (or anything else!) climate will change.
Here Jim talked about the Earth Radiation Budget Experiment briefly.
Energy balance and greenhouse gases
Radiation is characterized by its direction of propagation and frequency . We need to know about electromagnetic spectrum, and for climatology (look at Pierrehumbert's book, p137) we need infrared through ultraviolet.
Some quick notes from Esther Widiasih's talk at the MAA North Central Section summer seminar on climate modeling -- thanks again to the MAA and MCRN for sponsoring the workshop!
Start with the Budyko's energy balance model (EBM) -- a linearized version:
with equilibrium solution
This equilibrium is stable with eigenvalue (recall ).
What if the earth’s albedo was not ? Remember, albedo of ice is , so changing ratios of ice to land to water change overall albedo.
Next step: zonal energy balance models.
The MAA North Central Section is having a summer short course on climate modeling. This morning we've started out with an overview of climate and climate modeling by Samantha Oestreicher. We'll be alternating between lectures and hands-on computer modeling.
I'll be trying to live-blog it, more or less.
Here goes! Some notes from Samantha's talk.
What is climate? Climate versus weather: "Do I need to own an umbrella?" versus "Do I need an umbrella today?"
How do we observe climate? Data comes from many sources: