Point of View

By: Dr. Ricky Rood , 6:03 AM GMT on August 23, 2012

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Point of View: Models, Water, and Temperature (6)

This is a series of blogs on models, water, and temperature (see Intro). I am starting with models. In this series, I am trying to develop a way to build a foundation for nonscientists to feel comfortable about models and their use in scientific investigation. I expect to get some feedback on how to do this better from the comments. In order to keep a solid climate theme, I am going to have two sections to the entries. One section will be on models, and the other will be on a research result, new or old, that I think is of particular interest.


Doing Science with Models 1.3: In the previous entry of this series I used the example of balancing a monthly checking account to make the point that studying the Earth’s climate is very much like balancing a budget. Rather than money, we calculate a budget of energy.

Energy is one of the attributes used by scientists to describe the physical world, and it is a basic law of classical physics that energy is conserved. There are the laws of conservation of energy, conservation of mass, and conservation of momentum. Momentum describes how an object is moving: its mass, its speed, and its direction.

I introduced the concept of making a mathematical representation of the real world with this equation for money

Today’s Money = Yesterday’s Money + Money I Get – Money I Spend

and I came to point where I said we have a similar equation for energy

Earth’s Energy Today = Earth’s Energy Yesterday + Energy Gained – Energy Lost

These equations are the most basic models for the process that they describe. In fact, these equations could be said to be the perfect model for your personal budget of money or the Earth’s budget of energy. In the jargon of the scientist who builds models, this perfect model is often called the “analytic” model because it can be solved exactly, or analytically, by arithmetic.

The next idea I want to introduce is point of view. In the first instance, above, the equation represents a personal budget. In the second instance, the equation represents the energy budget of the whole Earth. Recall in the previous entry when I set up the problem of looking at the Earth’s energy, I said to imagine a person not on Earth, but who is observing the Earth. The observer, perhaps on Mars, sees the Earth as a small dot with energy coming in from the Sun, which the Earth then emits back to space from the Earth. If the Earth is in an energy balance, then the amount on energy coming back to space equals that coming in from the Sun.

That’s interesting to think about for a minute. Let’s assume that the Sun is constant. Then if the Earth is in an energy balance, the energy coming back to space is the same no matter the amount of carbon dioxide in the atmosphere. So to the person on Mars, the Earth would look the same. But the conditions on Earth might be quite different if the atmosphere had 600 rather than 300 molecules of carbon dioxide per every million molecules of air. This is because the point of view that we are interested in is from the surface of the Earth.

In 2010 I had a series of blogs called Bumps and Wiggles (here, go back and give it some “likes”). In the third of that series, I introduced Simple Earth. Here is that figure, which is described more completely in the original blog.





Figure 1: Simple Earth 1: Some basic ingredients of the Earth’s climate.

The problem of climate and climate change is important because of our point of view. If we are to continue to build thriving economies in our societies, we need a stable climate. In this case, stable really means that we know what to expect. Therefore, the climate of the Earth that might be of interest to that person sitting on Mars is not especially relevant to the person sitting on the surface of the Earth. Therefore, we need to think of models that are from the point of view of the person on the surface of the Earth. Again, energy and the law of conservation of energy come to the forefront.

In the figure, if the stick man looks around there is energy everywhere. It comes as heat from the Sun. It comes as wind from the air. It comes as waves from the sea. It comes as food from the land. So the accounting problem becomes more complex. We need the budget of energy for the atmosphere, the oceans, the land, and the glaciers and ice sheets. This energy needs to be balanced with what comes in from the Sun and what goes back to space. It is the same simple-to-conceive classical physics, but since we are in the middle of it all, the problem becomes complex. Still though, it is only a matter of balancing the books.

Interesting Research: Warming and Cooling in Ice Sheets - I’m usually not the blogger reporting on the most recent papers and breaking research, but this week I am different. The paper is Recent Antarctic Peninsula warming relative to Holocene climate and ice-shelf history, which was published online on August 22, 2012 in Nature. Robert Mulvaney is the senior author. The press take on this paper is that ice-core data show that over the previous, approximately, 12,000 years (the Holocene), there have been a number of times when there has been warming on James Ross Island, an island off the Antarctic Peninsula. These periods of warming have been comparable to the warming observed in the last 50 years, and hence, there are examples of warming that are not caused by the recent increases in carbon dioxide. There are scientific and political consequences of this paper. I will try to think like a scientist.

What does this paper say about generalized warming of the planet due to green house gases? First, we have to look at the locality of the data. It is from a single small island, in a part of the world that is known to have substantial fluctuations of temperature. We then need to look at how this knowledge fits in with the body of evidence as a whole. For example, Mulvaney and coauthors found a prominent warming period about 600 years ago. Was this warming at James Ross Island accompanied by warming of the same global extent as the currently observed warming? Are there other existing data that suggest natural internal variability during these previous times of warming? Is there something different in the past 50 years that distinguishes the current warming from the previous times of warming? The list goes on. So this result needs to be placed in context of all of the data and knowledge, and the coherence of this new information with the existing information needs to be evaluated.

This paper highlights the difficulty of extracting the contribution of warming due to carbon dioxide increase for any particular event. Ages ago, I had a blog on the breakup of the Larsen Ice Shelf. This new result makes the easy attribution of that ice-shelf collapse to human-caused warming difficult. As above, that attribution problem requires looking at the ice- shelf collapse in concert with other information. Was the event isolated? Is there evidence of other causes of variability? Is there something now that is different from the past? One attribution question that I can see – can the extra warming from carbon dioxide push the melting of the ice shelf over a tipping point?

Finally, I will bring us back to models, as models are ubiquitous in climate science and science in general. Within this paper, a glaciological model is used to determine the age scale. This model represents the flow of ice in the glacier, and that flow is assumed to remain constant over the time of the study. Another place that a model is used is determining the temperature based on the observations of isotopes of oxygen. This requires a melding of theory and application. Therefore, when you say, “but the observations show …” remember the role of models in making those observations.

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Nan

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Perhaps you have read some of the "Climate Change SOS" blogathon on the Daily Kos site this week.

There is a poem read by the author called "What Did You Do Once You Knew" which I thought I would share.

http://www.dailykos.com/story/2012/08/22/1122834/ -Climate-Change-SOS-Wednesday-What-did-you-do-once -you-knew

Nan
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Member Since: August 24, 2010 Posts: 0 Comments: 4838
Way to be up to day on the article!

The news was also talking about Dr. Angel's plan to block 2% of the light hitting earth, to cool it back down in the news today. (last resort)
That goes well with your model explanation.

The confusing part to me was the elevated CO2, NOT trapping extra energy and upsetting the energy budget for the martian observer.
Or the arctic sea ice melting and the water absorbing what the ice used to reflect. That throws the simple global energy balance out of wack too.
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The International Energy Agency said the U.S. has cut carbon dioxide emissions more than any other country over the last six years. Total U.S. carbon emissions from energy consumption peaked at about 6 billion metric tons in 2007.

Before someone starts claiming that it's the economy and lower generation numbers, lets' check those numbers.

Total electricity generation 2007 4,156,745 thousand MWhs.

Total electricity generation 2011 4,105,734 thousand MWhs.

Percent change -1.2

Here are some other 2007 to 2011 percentage changes:
Coal -14.0
Petroleum -75.9
Natural Gas +13.4
Other Gases -16.2
Nuclear -2.0
Hydroelectric Conventional +31.3
Non-hydro Renewables +85.3

It's not a huge drop in production. Mostly the decrease in CO2 emissions are due to a significant move from coal to natural gas. Petroleum was not a major player.

Non-hydro renewables are still a very small part of our energy supply but they are starting to take off. Wind is likely now over 4% of total generation and solar installations were up 85% in the first quarter of 2012 over first quarter 2011.

Seems to me that the great ship has reversed course and started a slow movement in a better direction.

(We've got an opportunity to help it along coming up in a couple of months. Do what you can.)
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With respect to models, the very science behind the Mulvaney et. al. paper is based on the same mathematics as Dr. Rood's budget model:

(Oxygen Isotopes in Sea Water) - (Lighter Oxygen Isotopes lost to evaporation from heating) = (Heavier Oxygen Isotopes remaining in Sea Water).

When those isotopes are trapped and stratified in the snowpack, it can create a robust temperature proxy over time.

Even with this proxy, it always concerns me when the general public focuses only on actual temperature numbers rather than looking at how those temperatures change over time. What I enjoy about the Mulvaney et. al. paper (as well as most peer-reviewed climate papers) is that they discuss warming in terms of rates, which is indicative of trends. In summary, some points they found:

- Warming trends at the study site exceeded 1.25 deg C per century from AD 296 to AD 415.

- No temperature signal was detected for the Little Ice Age (~ AD 1410).

- The rate of temperature increase from AD 1400 to AD 1850 at the study site was 0.22 (plus/minus 0.06) deg C per century.

- During that interval, the warming trend exceeded 1.5 deg C per century between AD 1518–1621 and AD 1671–1777.

- Over the past 100 years, the mean temperature at the study site increased by 1.56 (plus/minus 0.42) deg C (the fastest over the past 2,000 years).

- The recent warming at the study site began in the mid 1920s and, the temperature has risen at a rate equivalent to 2.6 (plus/minus 1.2) deg C per century for the past 50 years.

Was their work indicative of global trends? Since they failed to find a signal for the little ice age, I would say no. However, as Dr. Rood wrote, their work was from one study site in the Antarctic, and so my personal take home message is this: Past warming trends in this part of the Antarctic have contributed to ice shelf instability in the past. Therefore, current warming will likely contribute to ice shelf instability in the near future. From there, it's up to us about how subjective we want to be about the current warming. Though, even the paper suggests what should be obvious to most:

"If warming continues in this region, as is suggested by its attribution in part to rising atmospheric greenhouse gas concentrations, then temperatures will soon exceed the stable conditions that persisted in the eastern Antarctic Peninsula for most of the Holocene. The association between atmospheric temperature and ice-shelf stability in the past demonstrates that as warming continues ice-shelf vulnerability is likely to
progress farther southwards along the Antarctic Peninsula coast to affect ice shelves that have been stable throughout the Holocene, and may make them particularly susceptible to changes in oceanographic forcing."
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The International Energy Agency said the U.S. has cut carbon dioxide emissions more than any other country over the last six years. Total U.S. carbon emissions from energy consumption peaked at about 6 billion metric tons in 2007. Projections for this year are around 5.2 billion, and the 1990 figure was about 5 billion

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China to spend $372 billion on cutting energy use, pollution

China, the world's biggest emitter of greenhouse gases, plans to cut its CO2 emissions per unit of GDP by 40-45 percent from 2005 levels by 2020.

Over the past few years China has phased out thousands of old, inefficient factories and fossil fuel-fired power plants while becoming the world's biggest producer of renewable energy.

However, greenhouse gas emissions continue to rise, and according to a recent report, China's carbon output grew by 800 million tonnes to 9.7 billion last year, or 29 percent of the world's total CO2 emissions.

Government officials said they expect China's greenhouse gas emissions to peak around 2030.


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We wring our hands about nothing being done, perhaps we aren't looking closely enough....
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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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