National Academy of Sciences President Cicerone Links Energy Use to Global Climate Change

Holly Welles ・ High Meadows Environmental Institute
Ralph Cicerone
Ralph J. Cicerone, U.S. President of the National Academy of Sciences, delivering the PEI 2011 Taplin Environmental Lecture. (Photo: Brian Wilson)

In an effort to provide clarity to a topic often misunderstood by the media and the general public, Ralph J. Cicerone, the U.S. President of the National Academy of Sciences, presented the scientific basis for the earth’s changing climate while delivering the Princeton Environmental Institute’s 2011 Taplin Environmental Lecture on April 7, in Guyot Hall.

In introducing Cicerone to an overflowing audience, the Director of the Princeton Environmental Institute Steve Pacala said, “In my view, there is no greater issue today, more at the intersection of science and politics than climate change…At no time in my life, certainly, have non-scientific claims about the veracity of scientific information gained more traction in Washington, D.C., than they do today. But in the end, I believe that it is the scientific information that will be decisive.”

During his lecture titled “Global Change: A Scientist’s Perspective,” Cicerone provided recent climate data and other evidence directly linking anthropogenic fossil fuel emissions to changes in the earth’s climate. He presented data gathered over the last few decades showing warming air and ocean temperatures, decreasing amounts of polar ice, and rising global sea level. To explain these observations, Cicerone introduced the concepts of the earth’s energy budget and the “greenhouse effect,” whereby heat absorbing gases effectively warm the atmosphere. He referred to data indicating that, before the industrial revolution, incoming solar radiation was in balance with outgoing infrared radiation, causing the earth’s energy budget and resulting climate to be fairly stable. But since the beginning of the Industrial Revolution, when humans began adding unprecedented amounts of CO2 and other greenhouse gases into the atmosphere, the balance has tipped causing more heat to be trapped in the atmosphere and the globe to warm.

Noting that several other greenhouse gases, including nitrous oxide and methane, are following the same pattern as CO2, Cicerone said, “The carbon dioxide increase measured in the last two decades has given rise to an extra [approximately] 1.6 watts per square meter of energy being trapped near the earth’s surface, the methane increased about a half a watt and nitrous oxide about two tenths.” He went on to describe the global distribution of sea surface and atmospheric temperature anomalies and noted that, “Over the oceans, there’s much less warming. No surprise, because the waters have very high heat capacity. The marine areas are warming up more slowly, the land areas more quickly. In fact, they’re warming up quite a bit more quickly.” He said that a lot of the excess heat being trapped at the earth’s surface due to the extra greenhouse effect is flowing into the world’s oceans, but that this trend is not yet measured well and needs further research.

Cicerone explained, “A group at Oak Ridge National Laboratory [has done] a very careful job of keeping track of all emissions of carbon dioxide and fossil fuel burning over the past 250 years…we are now emitting about 8.5 billion tons of carbon in the form of carbon dioxide into the atmosphere just from fossil fuel usage. Whereas 100 years ago, it was less than 1% of that number and this number is rising quickly.”

Ralph Cicerone slide presentation
Cicerone illustrates the global land and ocean temperature index between 1880 and 2010. (Photo: Brian Wilson)

Cicerone described how the renowned Keeling Curve shows the steady rise of atmospheric CO2 year after year. He noted that when Charles Keeling began measuring the concentration of atmospheric carbon dioxide in 1958 at the Mauna Loa Observatory in Hawaii, there were 312 parts per million of CO2 in the atmosphere and now the number is about 390.  Cicerone  said that even by the 1980s, increases in atmospheric CO2 were alarming scientists.

“What’s different about this last 30 years is it’s completely outside the range of all previous thermometer measurements. The rate of increase is greater than anything we thought of. And it’s also larger than any of the models can assimilate with purely natural causes. The last 30 year period is the only time in human history when we’ve measured the output of the sun well enough to be able to say yes or no; is the sun causing these changes?” Based upon these measurements Cicerone stated, “the sun is not causing the recent climate changes.”

The pattern of energy usage in the world is shifting toward developing countries. As the world energy usage grows, the U.S. fraction is decreasing. So if we decide to manage carbon dioxide somehow, “we need to be aware of these changes,” said Cicerone.

Using a bathtub as an analogy to the atmosphere, Cicerone explained that approximately 8.5 billion tons of carbon dioxide are being added into the tub each year just due to the burning of fossil fuels (see Figure 1). “Meanwhile, the earth’s natural ‘sinks’ — the oceans and land together — can absorb about half, leaving the remainder to accumulate in the tub each year. “So if we want to stabilize the water level in the bathtub, we have to either increase the ability of nature to take up the carbon dioxide or decrease the flow in…this is the bottom line. It’s these numbers now that are the basis for people saying that if there were a desire to stabilize carbon dioxide amounts, it’s not enough to stabilize emissions, and have constant emissions which intuitively you may think would do the job. It doesn’t because as long as the emissions exceed the drain down capacity, the carbon amounts will continue to grow.” Hence, more CO2 will accumulate in the atmosphere resulting in an enhanced greenhouse effect. He said, “In fact, carbon dioxide emissions would have to be cut two-thirds to be able to stabilize the water level.” He emphasized that he had not even added in the carbon dioxide being added by land use changes and deforestation.

Figure 1
Global carbon cycle management

Ending with one final observation, Cicerone said, “Twenty years ago next year, there was the creation of the United Nations Framework Convention on Climate Change which President Bush 41 signed, as did most national leaders. And one of the important provisions there said the objective of this conference, and all the machinery they set up through this UNFCCC, the Framework Convention on Climate Change, was aimed at preventing dangerous human interference with the climate system. But they didn’t define what dangerous means. So the question is, who should define dangerous, and should this be a role for the scientific community also? Or is this a decision that should be based completely by a broader spectrum of the public?”

The overflowing audience attending Cicerone’s lecture in Guyot 10.
The overflowing audience attending Cicerone’s lecture in Guyot 10. (Photo: Brian Wilson)

After the lecture Pacala remarked, “Cicerone communicates with clarity and candor. He is the master at connecting the dots through the scientific evidence which is much more persuasive than a “call to arms.” Cicerone’s speech and slide presentation are available online.

Endowed by Frank Taplin ’37, the Taplin Environmental Lecture Series at the Princeton Environmental Institute was established in 1997. The Taplin Series brings accomplished scholars and other environmental leaders from industry, government, NGOs, and the private sector to the Princeton University campus to give lectures on a range of topics including environmental ethics, federal land use policy, and the role of science, technology and industry in environmental mitigation.