The Big Picture of Climate Change Science

by Mark Marchand on March 9, 2012

Since my early days studying complex organic molecules in college to today as I sort through myriad sources of information on news websites, blogs, and elsewhere,  I have often forced myself to step back and examine the “big picture” to obtain a better understanding of an important topic.

A recent lecture on climate change here at Rensselaer presented such an opportunity. Hosted by School of Science Professors Bruce Watson and Mimi Katz, the lecture before a packed room in the Amos Eaton building had a simple but noble goal: present some of the vast body of scientific evidence that supports the overwhelming conclusion that our climate is changing and warming at an accelerated rate, and the primary cause is anthropogenic, or related to human activity.

The special lecture was designed to help attendees—including fellow faculty members, students, staff, and others—navigate some of the misinformation and misleading information emerging from political and ideological discussions so prevalent today. It will be impossible to cover all that Watson and Katz discussed, but here’s some highlights.

As he is known to do, Watson—a respected, well-published member of the Earth and Science faculty, an Institute Professor, and a member of the National Academy of Sciences—set the stage in his low-key, friendly, and informative introduction. Climate science boils down to four broad questions, he said, which help us understand the scientific evidence supporting climate change conclusions:

  • How has our planet responded to perturbations—or naturally occurring alterations/changes—in our geologic past?
  • What role do solar system factors—such as observable variations in Earth’s orbit and rotation—play in changes in solar energy output over time?
  • What can global climate models tell us about the future?
  • What are observable trends in real time and in the more recent geologic past, such as up to one million years ago? (This is where some of the glacial ice core studies come into play; but more in a bit)

Together, these four questions lead to sub disciplines that have helped scientists reach their conclusions.

Further, Watson challenged the audience, everyone should be skeptical when they read or hear about climate change—but just as important is the need to seek information from vetted sources and qualified individuals . . .and be receptive to views that you don’t even want to hear.

An important question, Watson asked, was why respected scientific organizations such as the American Physical Society, the National Academy of Sciences, the American Geophysical Union, and many other organizations around the world take the stand they have on climate change? He suggested that these organizations were not populated by “scientific sheep.” Rather, their stance on climate change and the role of human activities is based on a vast body of solid scientific evidence – all pointing to the same conclusion.

Katz, who published a recent paper on her research dealing with ancient Antarctic currents and their roles in global climate changes, presented some of the scientific evidence on climate change.

One of the topics she covered was the increasing amount of carbon dioxide—the primary “greenhouse” gas responsible for warming temperatures—in our atmosphere. Drawing upon ice cores dating back almost a million years, scientists can easily measure the atmospheric concentration of carbon dioxide at specific times. While levels have risen and fallen over thousands of years, we began to see an unnatural spike in the 19th century, at about the same time a more modern and expanding society began widespread land clearing (see chart below). This was done to obtain building materials, to create space for farming, and to acquire fuel. This has even continued today, through the clearance and burning of tropical rain forests. Near the end of the 19th Century, however, the levels of carbon dioxide spiked sharply—at about the same time the burning of fossil fuels for heat, energy, and transportation took off.

While many won’t disagree with the evidence of sharply higher levels of carbon dioxide, some who fervently disagree with the conclusions of some 98 percent of scientists say the increased levels come from natural sources such as volcanoes and other active geothermal phenomena. Not so, says Watson, who explains that scientists have easily traced the source of most of the atmospheric carbon dioxide, using a process known as isotopic analysis, to the burning of fossil fuels.

The chart below focuses on a gas known as methane, an even more potent greenhouse gas that also oxidizes into carbon dioxide in 10 to 12 years.  While there are always some natural sources—wetlands and termites account for about 30 percent of the natural sources—the sources related to human activity (anthropogenic) account for 70 percent. Of that amount, fossil fuels represent the largest single factor.

Here’s another chart from Katz’ talk. Combining observed data such as ice core sampling from hundreds of thousands of years ago as well as scientifically proven global climate models, Earth’s temperature changes correspond closely with carbon dioxide concentrations, rising and falling with ice age and interglacial cycles. While it’s a little tough to see, the spike in the blue-green line near the vertical axis on the far right is where we are today. This severe and unexpected spike is pulling temperatures up at a time when, both Watson and Katz explain, most scientists would be expecting a cooling period . . .or even a mini ice age.

Here’s another look at the expected, natural temperature trend toward cooling and glaciations, versus the actual trend we’re witnessing today. What’s interesting is the somewhat troubling notion of fossil fuels being depleted in the not-too-distant future, and the resulting temperature decrease toward the expected cooling period.

There’s much more, ranging from empirical evidence on sea levels rising to ice sheets over Greenland melting to the decline of Arctic sea ice. According to Katz and Watson, a good place to examine a lot of the good science on the topic is the National Academies of Science site I listed earlier, repeated here.

The science is good and, as the national academy points out, it poses significant risks for all of us, on environmental, economic, and humanitarian fronts. While no one can be absolutely precise on the future risks, the NAS says there are prudent reasons to act now to control and reduce the emission of greenhouse gases, lowering the risks posed by climate change.

My thanks to Bruce and Mimi for a great lecture.


Dave Aiello 03.12.12 at 5:28 pm

Ivar Giaever resigned from the American Physical Society over the policy statement it made, specifically, \"The evidence is incontrovertible: global warming is occurring.\" If Dr. Giaever were just some Nobel Prize winner who spoke at Rensselaer once, that would probably not merit his mention in a post like this one. However, he is a Nobel Prize winner and an Emeritus Professor at Rensselaer.

Since the lecture apparently cited the American Physical Society\’s policy statement as one justification for the discussion of Climate Change, I think any lectures referencing that statement ought to recognize Dr. Giaever\’s position and address it.

I\’m more than willing to hear these professors out on their reasons for supporting the notion of Climate Change. How do Drs. Watson and Katz reconcile their positions with that of Dr. Giaever? Do they think Dr. Giaever is incorrect in his conclusions?

Vacation Rentals Virginia 03.13.12 at 9:55 am

Scientists community, government and ecologist should think about some serious measures to be taken in order to prevent global natural cataclysms with some serious consequences for the human kind. We still have time to back things to normal to some extend, but we need some common efforts to be made in order to do it.

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