Deep Time and Climate Change

One of the interesting things about studying Earth's past is just how tremendous the changes have been, and how much we can learn about the earth system by studying them.  In many cases they provide our only insight into what we can expect from future climate changes.  We can look at past forcings and responses in the earth system and ask what happens when the oceans become acidified, or when CO2 exceeds 400 ppm, or even more.

We spent some time talking about past climate change, but most of what we looked at was in the last 65 million years (myr).  This sounds like a long time, but it is just a hair over 1% of Earth's history. Check out this report from the National Academy of Science about climate change in deep time.  You can read it online below, or download the PDF.

Deforestation, Maya, and Climate Feedbacks

In class we've been learning about climate forcings and feedbacks, and we often think that these are effects that operate only at very large spatial scales.  But the Maya found out the hard way that human modification of landscapes has repercussions on the climate system.  Check out these results from a NASA climate simulation.  It shows how changing the land cover feeds back on the local climate system.  When you are looking at the figures and reading the explanations, think about things that we covered, like albedo, latent and sensible heat, transpiration, etc.  It will help reinforce the concepts we covered in class, and show how it matters in the real world.

Also, continuing on the forcings and feedback discussion that came up in class today about greenhouse gasses, here is a nice overview site of the roles of non-condensing greenhouse gasses, particularly CO2, in climate forcing, and water vapor and clouds as feedbacks.  Again, picking up on the material covered in class today, it shows how you can use climate models to perform virtual experiments on the earth system.  If you want to try this yourself, see the edGCM in the previous post.