Dr. Ricky Rood's Climate Change Blog

Volcanoes and Long Cycles - Bumps and Wiggles (4)

By: RickyRood, 4:19 AM GMT en Abril 28, 2010

Volcanoes and Long Cycles - Bumps and Wiggles (4):

Introduction: This is the fourth 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. The volcano in Iceland and the end of the semester have thrown me off track.

Comments to the last couple of blogs have included one of the usual type that all of climate change is due to “cycles,” as well as a statement that the Icelandic volcano, Eyjafjallajökull, had put an enormous amount of carbon dioxide into the atmosphere. Both of these statements were meant, I presume, to imply that the emissions due to burning of fossil fuels was either inconsequential or that we were at the fate of powers that are out of our control; hence, we should march on our merry ways. Well … ?

First on the emissions that come from volcanoes – I wrote to Alan Robock at Rutgers University to ask him about Eyjafjallajökull. Alan is my go to scientist on volcanoes and I use material from his research in my class. He sent me a good web link for current information on the eruption.

On very long time scales volcanoes, or more generally, emission of CO2 by out gassing from the Earth is very important. Again on geologic time scales, millions of years, out gassing from the Earth is balanced by formation of rocks.

When we consider climate change of the past 1000 years or so, we take into account volcanoes. In the absence of observations or theory to the contrary, we assume that, in our current temperate climate, volcanic activity is sporadic and the frequency of eruptions is not changing. With this assumption, we say that there is “no change” in volcanic activity, which is NOT the same as saying that volcanoes are unimportant. They are an important natural ingredient of the Earth’s climate.

Usually, when we think about volcanoes we think about them in terms of cooling the Earth. Explosive eruptions place particles or droplets with high concentrations of sulfate (SO2) into the stratosphere, above say, 18 kilometers altitude. These droplets are called sulfate aerosols; aerosol is the term used to characterize particles in the atmosphere. Sulfate aerosols in the stratosphere 1) stay there a couple of years, and 2) reflect sunlight back to space. (Gee, if I do an image search I find an ancient blog of relevance. No copyright issues with this figure.) This is expressed schematically in the figure below.

Figure 1: The role of aerosols in the Earth’s climate.

On the time scales of a few years, say 5, we don’t usually concentrate on the role of CO2 emitted from volcanoes. One of people who commented on my blog said that “40 years” worth of CO2 had been emitted by Eyjafjallajökull. I know of no observational evidence or theory to support this assertion. In general, the CO2 emission by a single volcano is not significant enough to cause a substantial bump in the carbon dioxide data. Here is the current figure of the Mauna Loa CO2, from the excellent Earth System Research Laboratory web site on CO2 trends.

Figure 2: Up to date times series of CO2 at Mauna Loa.

I use this figure to point out that the explosive eruptions of El Chichon (1982) and Mount Pinatubo (1991) did not change this curve in any easily perceptible way. (You can find tables of numbers on this web page.) If you think about the enormous eruptions of Krakatoa and Tambora, we associate these with documented cooling from the aerosols, but not with surges in long-lived CO2 increases.

It is simply not true that current volcanic emissions in anyway compare with or overwhelm emissions from burning fossil fuels. We will see what the global record brings us in the next few months. It will be interesting to compare the emissions from the volcano with the reduction of emissions by grounding aircraft.

But the ideas about climate cycles did get me thinking, and my thinking was placed into a different context by the geologist Henry Pollack. Henry has a new book called A World Without Ice. This is a very well written book, which I strongly recommend. I was at an event with Henry where he pointed out that humans today are the largest geological force altering the surface of the Earth. (I can’t help think of the oil flowing into the Gulf of Mexico. We open it up and take it out.)

It is true that the Earth’s climate experiences cycles and perhaps jumps from one stable-for-a-while climate to another – on geologic time scales. But these jumps do not absolve us from our role; they aren’t unexplained magic. The jumps in climate are associated with large changes in greenhouse gases, especially carbon dioxide and methane. Large jumps in greenhouse gases are associated with either geology, absorption by and emission from the ocean, or changes in life. Changes in life? Plants and animals exist in a balance and cause a tension between carbon dioxide and oxygen. Life is a crucial controller of atmospheric composition. Humans are the current dominant life form, and we are a dominant geological force.

Yes the climate cycles. We know that the cycles generally have great shifts in greenhouse gases. Right now, we are the life, the force that is causing a great shift in greenhouse gases. We dig and pump and burn. It is convenient to say that the climate cycles, but this is the only cycle that has ever had us in it. With the knowledge that we have of the role of greenhouse gases in climate change, we have a wonderful opportunity and knowledge to perhaps start to manage the cycles and maintain a planet that is sustaining for our particular form of life. Otherwise yes it is a cycle and on the epochs of cycles it’s the time when some life form decided to burn stuff.


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

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Simple Earth - Bumps and Wiggles (3):

By: RickyRood, 7:02 PM GMT en Abril 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)

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Some Jobs for Models and Modelers

By: RickyRood, 3:34 AM GMT en Abril 03, 2010

Some Jobs for Models - Bumps and Wiggles (2):

Introduction: This is the second 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.

Back in October I wrote an entry about a paper by Judith Lean and David Rind. They take a position on predictability of a measure of “global warming” on a decadal time scale. This is based on an analysis of past natural variability and the assumption that that variability extends into the future. Another recent paper by Keenlyside et al., 2008 in Nature, examines the impact of the variability in the Atlantic Ocean on regional and global climate. Keenlyside et al. project that based only on the projection of the observed Atlantic variability into the future, natural cooling will act counter to the projected human-made warming. Lean and Rind assert that their analysis suggests warming even in the presence of this projected cooling. These are both statements that will be subject to “validation” with observations.

Here is Figure 1 from Lean and Rind:

Figure 1 from Lean and Rind (2009), Geophysical Research Letters. Figure taken from tinypic.com. This figure shows the temperature record and the model representation from 1980 to 2030, the subject of this series of articles.

As we think about the development of climate services and the development of policies to manage, essentially, the average temperature of the planet, it is imperative that we start to understand all of the bumps and wiggles in this curve. It will no longer be adequate to say, simply, that the differences between observed warming and predicted warming are “well within” the normal observed variability.

How do we do this? First the problem needs to be broken down.

In the past few weeks I have seen some outstanding presentations by Professor V. Ramanathan from the University of California San Diego. (I recommend specifically this part of Ram’s web page.) In his talk he started by posing the question of why the warming of the Earth’s surface has not occurred as rapidly as predicted. This question requires following the heat. The answer lies in the ocean, where the heat is not only increasing, but it is increasing at different rates in the different oceans. This difference, due to how circulation varies from one ocean to the next, is predicted by model simulations. (See here) (Does it make sense that if the ocean can take up heat then it can give it back?)

So if we look at the differences between a climate projection and the subsequent observations, then there are a variety of possibilities of why the prediction might be in error. In the case of the previous paragraph, not all of the heat went into the surface air temperature. Another possibility is to look at the details of the ultimate source of the Earth’s energy, the Sun. As many of this blog’s readers know, the Sun had a very long sunspot minimum, suggesting a decline in the energy coming from the Sun (see here - It’s time for a solar update.) If we are going to thoroughly explain the differences between predictions and observations, then we will need to quantify, better, our knowledge of the output of the Sun.

The effort to quantify the difference between the predictions and observations reveals errors and inadequacies in the models (and the observations) that need to be addressed. So far in this article, we see the need to better represent the coupling of heat transfer between the atmosphere and the ocean as well as our observations and ability to model the Sun. There are those who would say that the presence of such errors means that the models are not up to the task. There are others who see the identification of errors as the opportunity to improve the models and the quality of predictions.

Explicit identification and correction of errors has been one of the best strategies for improving weather forecasts. During the 1990s, the scientists at the European Center for Medium Range Weather Forecasts (ECMWF, the leading forecast center), started to focus on forecast busts and trying to identify the cause of busts. (A dense presentation on the subject) This has been so successful that methods to identify, automatically, sources of errors have been developed. (see learned article from a different Jim Hansen and Emanuel). For errors to be useful to guide incremental improvements to models and observing systems, the forecast has to have enough skill to provide a worthy estimate to start with. We are at that stage.

Climate modeling, prediction, and validation are moving into a new era. The projections and the validation of those projections are good enough to say definitively that the Earth will warm, sea level will rise, and the weather will change. This is actionable information; we need to prepare for this. We need to try to manage the warming to keep it from getting too large; we have stated in the Copenhagen Accord that we will keep warming to two degrees. Our models are not up to that task. Striving to understand the bumps and wiggles as a forecast problem will identify errors that will be corrected, improve the quality of the models, define the need for new observations, and set the foundation for meaningful predictions on decadal scales.


Bumps and Wiggles (1): Predictions and Projections

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Faceted Search of Blogs at climateknowledge.org

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Dr. Ricky Rood's Climate Change Blog

About RickyRood

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.

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