I'm a professor at U Michigan and lead a course on climate change problem solving. These articles often come from and contribute to the course.
By: Dr. Ricky Rood , 7:02 PM GMT on April 11, 2010
Simple Earth - Bumps and Wiggles (3):
Introduction: This is the third in a series on understanding climate variability, global warming, and what we might do about it. The series focuses on the past 30 years and the next 30 years. This article is a bit of a restart; I feel I jumped the gun. Plus, of course, I think I have an important story that needs to unfold.
In the previous articles, see links below, I wrote that we are moving to a time when climate models will be used for more than providing guiding projections about how the Earth will respond to rapidly increasing greenhouse gases. The mantra in the field is to talk about decadal forecasts; however, the state of our observations and understanding of decadal variability are far from supporting a robust forecast of accurate spatial patterns of warming (and perhaps regional cooling) on times scales of decades. One focus that I pose is attention to the variability on, for example, the five year time scale for the last thirty years, now, and the next ten to thirty years. Bringing a focus to this variability will bring closer attention to the mechanisms and processes that cause variability, and it is a simple matter of common sense, that when scientists pay detailed attention to something, then we usually learn a lot more about it. It is sometime difficult to decide on the priorities of what to pay attention to next.
In the previous blog, I focused on the Sun and oceans. In the spirit of clarity, I think that I need to take a step back and draw a picture. There are a couple of things that I repeat tediously to my students and one of them is to draw a picture. So I drew the following picture, Simple Earth 1. It’s not great art, but pretty good given my skill with the pen.
Figure 1: Simple Earth 1: Some basic ingredients of the Earth’s climate.
In the figure I suggest land, oceans, people (animals), and plants. Up in the sky there is the Sun, even with a few suggestive spots on it. The hard part was to draw the greenhouse gases, that is, the gases that hold heat close to the surface of the Earth. The most abundant greenhouse gases are water and carbon dioxide. The greenhouse gases are represented by the pastel pinkish and blue layer between the Sun and surface. I drew it a little red on the bottom because greenhouse gases hold heat close to the surface, and they make it cooler higher in the atmosphere. Hence, I drew them a little blue on the top.
There is a fact that is implicit when we talk about climate, climate change, and the impact of global warming on the Earth. That fact is that our focus is first and foremost on the surface of the Earth, and that that focus is overwhelmingly influenced by an interest in what happens to people. When we focus on the surface of Earth and people, then we, implicitly, even more strongly pay attention to the land and the atmosphere that is closest to people. This high level of attention to what is really only part of our planet’s environment, embedded in a much larger environment, strongly influences how we measure, define and add up all of the mechanisms that cause variability in our environment.
Even in Simple Earth 1, there is a lot of complexity, both explicit and implicit. If we are going to understand how the temperature varies where the person is standing, then we might, reasonably, expect: 1) there to be changes in the energy coming from the Sun, 2) changes in the greenhouse gases that hold heat close to surface, 3) transfer of heat between the atmosphere, land, and ocean. Or we can just stand in the shade of the tree.
We developed a lot of experience and intuition over the centuries. It gets hot in the summer and cold in the winter, and that is strongly related to how bright the Sun is. It’s a little more complicated, but we also developed some intuition about the transfer of heat between the ocean and the atmosphere; the climate in California, Oregon, and Washington, is far different from the climate between Texas and North Dakota. These two groups of states span the same range of latitude, and intuitively, have the same “amount of Sun.” The difference is transfer of heat from the ocean.
As we try to quantify the variability, with the ultimate goal of predicting the variability, we come up against the vast complexity that is only hinted by this figure. That it is complex does not mean that we cannot do the problem; though it is a convenient excuse to maintain that we cannot – and always supplies a seed of uncertainty and doubt. The importance of our environment combined with our ability to alter our environment demands more and more ability to quantify and anticipate the changes that we might expect – whether they be “natural” or “human caused.”
In the previous two entries of this series (linked below) I jumped the gun a little bit. In the first article I wrote about how we had evolved past the standard of merely stating that the observed, specific variability of “the moment” was or was not consistent with our previous experience. The take away message, we have to measure and quantify the specific cause and effect of the bumps and wiggles that we observe. In the second article I wrote about “following the heat.” Therefore we have to first consider “the source” of the heat, the Sun, and how that changes. Then we have to put ourselves into that point of view of the person standing on the land in the lower atmosphere and ask – is it getting hot like the models have predicted? Well, the answer is yes, but he have to be smart enough to realize that some of the heat goes into the ocean, so we have to check whether or not the ocean is getting warmer at the same time that it is getting warmer where we live.
In this simple, first thought, the ocean is a sink of heat, but that is completely defined by that implicit point of view of the land-dwelling person. When I was a child, literally, very smart people said that “global warming” would not be a significant problem because the ocean is large and it “would just absorb the extra heat.” Well, it does absorb heat, but it takes a while, so when we get back to that human on the land, trying to grow that tree, it might get pretty hot before the ocean takes up that heat.
Of course, there is a detail, an important detail, what if the ocean gives back that heat? There is no reason to expect the ocean to just take up heat. The oceans are always giving back heat. Just go to California, or Britain, or the northwest Russian coast, or Trinidad.
With this restart and Simple Earth 1, it makes sense to start to march more carefully through the Bumps and Wiggles.
Bumps and Wiggles (1): Predictions and Projections
Bumps and Wiggles (2): Some Jobs for Models and Modelers (Sun and Ocean)
And here is
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