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 , 04:08 GMT le 07 mai 2010
Still Following the Heat - Bumps and Wiggles (5):
Introduction: This is the fifth 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. There has been so much going on it has become a bit of a ramble, but it’s a blog – so.
The basic idea in this series is that climate model projections and observational verifications are precise enough to tell us with extremely high confidence that the Earth’s surface will warm because of increasing carbon dioxide. With this knowledge in hand, a new standard is evolving in climate modeling, which is more in the spirit of traditional weather predictions. That is, more specific information about what is going to happen at a certain place at a certain time. To reach this new standard, it becomes imperative that we better quantify the bumps and wiggles in the observations for the last 30 years and use this information to develop our prediction skills for the next 30 years. It is no longer adequate to simply say that – given the observed natural variability, that any discrepancies between existing projections and observations are, formally, small. That is, they are noise.
Improving our ability to diagnose the discrepancies between model projections and observations challenges all aspects of the scientific investigation of the climate. Better observations are needed to sample climate variability. Better models are needed, and in particular, we will have to quantify better how pieces fit together and interact. Pieces? When we develop hypotheses, theories and predictive models, we break the climate system into pieces. One piece might be the type of convective cloud that causes thunderstorms, and that piece has to fit together with all of the other pieces that make up the atmosphere. Then the atmosphere has to fit together with the ocean and the land and the glaciers and the ice sheets and the sea ice and the trees and the people – it is a big problem. An important and understudied (I assert) part of climate science is “how do the pieces fit together.” While we know a lot, if we are going to understand the bumps and wiggles, then we are going to have to know more. (And for those who want to say it’s just a theory.)
So we break down the problem, and so far in this series (all linked below), we have talked about the Sun and the carbon dioxide that comes from volcanoes and “following the heat.” Of these the most important is following the heat. This is important because if you take a simple look at the warming due to carbon dioxide, the observed warming of the Earth’s surface is not as high as predicted. So what is wrong? In the second blog of the series we followed the heat into the ocean. Broadly in the last 30 years the heat content of the ocean has increased, and that is a far more convincing measure of a warming planet than the surface air temperature measurements. I want to revisit this because of a recent perspective by Kevin Trenberth and John Fasullo, who, investigating the recent bumps and wiggles, ask the question - why isn’t the ocean warming even faster? There is still missing heat. But first a diversion.
In the third entry of this series I introduced Simple Earth. Read that entry if you want the full description of the figure. Below is the same figure, but there has been one thing added to the figure. Namely, the blurry, reddish line on the surface. What this line represents is that if greenhouse gases increase, then there will be warming at the surface. (There will also be cooling in, say, the upper troposphere.)
Figure 1: Simple Earth 2: Some basic ingredients of the Earth’s climate and surface heating.
I also argued in that third entry that in the end, we were truly concerned about climate, climate change and humans. Sure we can dismiss the current warming as some cycle, but that takes humans and human-care out of the picture, and it is in our best interest to always think about climate and climate change in a human context. So when we think about it in the human context, we start to wonder about the warming at the surface, and especially, at the surface over land. Of course most of the Earth’s surface is ocean, and heat goes into the ocean. That’s what I represent in this figure:
Figure 2: Simple Earth 3: Some basic ingredients of the Earth’s climate. There is heat going into the ocean. (This is simple Earth, so this is vastly over simplified heat transport.)
So this brings us back to Kevin Trenberth and John Fasullo. In Science Magazine on April 16, 2010, they have a Perspective, where they discuss missing heat. The point of their article is that if you look at the heat budget of the Earth from satellites in space, we can measure that the Earth is not currently in balance. Heat is staying on the planet; hence, it must be warming. If you focus on the past five years, then the planet is just not warming as fast as it should. They do not say that the basic conclusions that the surface of the Earth is warming and will warm more are incorrect. Again, neither they nor their data challenge those foundational results, but if you look at the details, the bumps and wiggles, then we have some work left to do to fully understand what is going on. They conclude that now that geoengineering is entering our discussion, we really must be able to understand these bumps and wiggles.
This heat will be found, probably in the deep ocean, where we don’t have such good observations. The discrepancy will be explained. It is, ultimately, better observations that Kevin Trenberth and John Fasullo call for. (The discussion of the paper in blogs amongst both scientists and politically motivated sorts is pretty interesting. ( 1 , 2 , 3))
During my career, I have been fortunate enough to have some scientific successes – figured out something new, helped build an algorithm that got some use, or figured out a technique that mattered. Each time the result seemed big and significant in the moment. It’s not long after getting such a result that it seems mundane, perhaps almost self-evident – why did it take so long to figure that out? This is a little of what we are talking about here. So when Trenberth and Fasullo say,
“So, although some heat has gone into the recordbreaking loss of Arctic sea ice, and some has undoubtedly contributed to the unprecedented melting of Greenland and Antarctica, it does not add up to anywhere near enough to account for the measured energy difference at the top of the atmosphere.” (Emphasis mine.)
They are looking at the next problem, the bumps, the wiggles. They, their analysis, their observations offer no serious relief from the warming, the sea level rise, and the changing weather.
Bumps and Wiggles (1): Predictions and Projections
Bumps and Wiggles (2): Some Jobs for Models and Modelers (Sun and Ocean)
Bumps and Wiggles (3): Simple Earth
Bumps and Wiggles (4): Volcanoes and Long Cycles
And here is
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