Storms of My Grandchildren (2 page)

Another decade later, on June 23, 1988, I was a witness, an official witness, when I testified to a Senate committee chaired by Tim Wirth of Colorado. I declared, with 99 percent confidence, that it was time to stop waffling: Earth was being affected by human-made greenhouse gases, and the planet had entered a period of long-term warming. Combined with an unusually hot and dry summer and the attention global warming was getting nationally and internationally, my announcement garnered broad notice.

It soon became apparent, though, that my testimony, combined with the weather, was creating a misimpression. Global warming does increase the intensity of droughts and heat waves, and thus the area of forest fires. However, because a warmer atmosphere holds more water vapor, global warming must also increase the intensity of the other extreme of the hydrologic cycle—meaning heavier rains, more extreme floods, and more intense storms driven by latent heat, including thunderstorms, tornadoes, and tropical storms. I realized that I should have emphasized more strongly that both extremes increase with global warming.

Therefore I sought one more opportunity to be a witness. Senator Al Gore provided that opportunity at a hearing in the spring of 1989. When I sent Senator Gore a note before the hearing, explaining that my written testimony had been altered by the White House Office of Management and Budget to make my conclusions about the dangers of global warming appear uncertain, he alerted the media, assuring that there would be widespread coverage of the testimony. Unfortunately, the message about the wet end of the hydrologic cycle was lost in the brouhaha. Mother Nature, however, responded four years later with a “hundred-year” flood, one that normally occurs only once a century, which submerged Iowa and much of the Midwest. They were hit with another “hundred-year” flood in 2008.

After my testimony at Gore’s hearing, I was firmly resolved to go back to pure science and leave media interactions to people such as Steve Schneider and Michael Oppenheimer, people who were more articulate and seemed to enjoy the process. But after another decade I made an exception and agreed to debates in 1998 with the global warming “contrarians” Dick Lindzen and Pat Michaels, because I had a clear scientific purpose: I wanted to present and publish a table of the key differences between my position regarding global warming and the position of the contrarians. My expectation was that the table’s specificity would permit future evaluation of our positions. I would use this table in my meeting with Vice President Cheney’s Climate Task Force in 2001.

So for more than a decade after the Gore hearing in 1989, I was able to stick strictly to science, turning down many opportunities to appear on documentaries and other television programs. It was that science that I would discuss with the Climate Task Force.

A
LARGE POLICE DOG WAS LED IN to sniff around the room—we presumed that it was checking for bombs. Vice President Dick Cheney was about to arrive. This was the first meeting of the cabinet-level Climate Task Force. It fell on my sixtieth birthday, March 29, 2001.

“Climate Working Group” was the phrase I remembered from the phoned invitation, so that was the title I put on the handout I brought to the meeting. There was no letter of invitation, and I was not given any paperwork at the meeting. Later, President George W. Bush and the media referred to this group as the Climate Task Force, so I will use that title here.

The Climate Task Force consisted of six cabinet members plus the national security adviser (Condoleezza Rice), the EPA administrator (Christine Todd Whitman), and Vice President Cheney as chairman. The cabinet members were Secretary of State Colin Powell, Spencer Abraham (Energy), Paul O’Neill (Treasury), Gale Norton (Interior), Ann Veneman (Agriculture), and Donald Evans (Commerce).

We were three scientists who had been requested to explain the current understanding of climate change and the role that humans might have in causing global warming. We were a bit nervous. This was surely the most high-powered group that any of us had spoken to.

When I arrived early that morning at the Department of Commerce headquarters in Washington, D.C., the venue for the meeting, I found the other two scientists, Dan Albritton and Ron Stouffer, hunched over a table looking at the charts Ron planned to show. Dan was advising Ron to reduce the amount of complicated material.

Albritton, director of the National Oceanic and Atmospheric Administration (NOAA) Aeronomy Laboratory in Boulder, Colorado, and about my age, was an old hand at presentations. He had long been NOAA’s chief spokesman for describing research on the effect of human-made gases on the stratospheric ozone layer. Stouffer, a decade or so younger, is a climate modeler at the NOAA Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey. Climate models are computer simulations of the atmosphere, ocean, land surface, and their interactions, which are used to study the dynamics of the climate system and how future climate may change.

The backdrop for this meeting was President Bush’s confirmation that the United States would not sign the Kyoto Protocol. “Kyoto” required developed countries to reduce emissions of human-made heat-absorbing greenhouse gases to several percent below 1990 emission rates. The main greenhouse gas is carbon dioxide, which is increasing because of the burning of fossil fuels: coal, oil, and gas. Deforestation contributes a smaller amount, about 20 percent, to the carbon dioxide increase.

The president’s refusal to sign on to Kyoto was expected. More important was the revelation on March 13 that the United States would not regulate carbon dioxide emissions from power plants. That decision was a heavy blow to environmentalists and scientists who realized that Earth’s climate was approaching a dangerous situation because of the buildup of atmospheric carbon dioxide.

Coal burning at power plants is the greatest source of increasing atmospheric carbon dioxide. It is also the source most susceptible to control. The decision not to restrict power plant emissions reneged on a promise Bush made repeatedly during the 2000 presidential election campaign.

Bush had pledged to include carbon dioxide in a “four pollutant strategy” to reduce the most damaging pollutants from power plants. That promise, together with the Clinton-Gore administration’s poor record in constraining carbon dioxide emissions, stymied Al Gore from raising the environment and climate change as an effective campaign issue. Given the razor-thin margin in the 2000 election, and the environmental awareness of Florida voters, it seems clear that Gore would have become president if it were not for Bush’s pollution-reduction promise.

Despite that backdrop, the fact that the Bush-Cheney administration was having these Task Force meetings suggested that it took the climate change issue seriously and wanted to learn more about it. The implication was that future policies were still open and could be influenced by scientific evidence.

The vice president abetted these impressions in his opening remarks and noted that Task Force meetings would be “principals only”—participants could not send representatives in their stead. Treasury Secretary O’Neill related that the previous afternoon he had met with President Bush, who had said that he wanted the United States to take a leadership role in addressing climate change, even though it would need to be via a route other than the Kyoto Protocol.

Colin Powell apologized that he would need to step out during this meeting for a phone discussion with Yasir Arafat. Rats, I thought—that was disappointing. I had tailored some of my planned remarks for the secretary of state.

I was hopeful that there was a good chance that the group as a whole would favor actions to stem climate change. Powell and Rice surely felt the anger of Europe, Japan, and other nations about the failure of the United States to ratify the Kyoto Protocol. They must also have realized the benefit, for national security reasons, of reducing our dependence on fossil fuels. Both the Treasury’s O’Neill and the EPA’s Whitman had made speeches about the dangers of global warming and the need for strong policies to reduce fossil fuel emissions.

On the other side, Energy Secretary Abraham had stated in a public speech on March 19 that the United States must add ninety new power plants each year, mostly coal-fired, for the next twenty years to meet the need for a 45 percent increase in electricity demand by 2020. Vice President Cheney strongly supported efforts to increase fossil fuel supplies, including the opening of public lands, continental shelves, and the Arctic for increased coal mining and oil and gas drilling.

Altogether it was unclear where the balance of opinion of the Task Force would fall. I thought it was realistic to think the scientific information we provided would aid their decision making.

Dan Albritton gave an overview called “Climate Change: What We Know and What We Don’t.” Each of his hand-drawn charts included a little “thermometer,” or confidence index, with fluid rising to a level between zero and ten. Our understanding that the natural greenhouse effect keeps Earth much warmer than it would be otherwise rated a “ten,” for example, while our ability to describe regional effects of global warming rated only a “three.”

The basis for Albritton’s presentation was a set of reports by the United Nations Intergovernmental Panel on Climate Change (IPCC), which was in the process of being published at that time. Albritton’s bottom line, consistent with the rigorous position of IPCC, was that the scientific community provided policy-relevant information but would make no statements about policy.

My presentation was titled “The Forcing Agents Underlying Climate Change.” Forcing agents are factors that affect the energy balance and temperature of Earth, such as carbon dioxide in the atmosphere. I began by noting that climate, the average weather over a finite interval, fluctuates without any forcing, because the atmosphere and ocean are chaotic fluids that are always sloshing about. There is no way to predict far ahead of time where and how big any particular slosh will be. But once we see a slosh coming, we can project how it will play out. That is what weather forecasting consists of—mapping the current sloshes and looking upstream at where the next ones are coming from. In winter in the United States, if the next slosh is coming straight down from Canada, watch out!

Yet, despite this unpredictable sloshing, if weather is averaged over a long enough time, the system is “deterministic,” that is, it responds to a forcing mechanism in a predictable way. For example, if we begin to slowly move Earth closer to the sun, we can be sure that Earth will become warmer. Not every year though, because chaos and sloshings also occur on greater time and space scales than local day-to-day weather.

One big, slow sloshing on Earth is the “Southern Oscillation,” in which surface waters of the Pacific Ocean at the equator oscillate between warm El Niño and cool La Niña phases. La Niña is caused by the upwelling of a large amount of water from the cold, deep ocean along the South American coast. The effect of El Niño or La Niña on global temperature and precipitation patterns is huge. This oscillation would make it hard to notice immediately an underlying global warming trend due to Earth moving closer to the sun, for instance. The ocean would eventually get warmer, but that would take time because the ocean is two and a half miles deep.

Of course, the subject of interest to the Task Force was not the hypothetical case of Earth being moved closer to the sun. Rather, I needed to discuss real climate forcing mechanisms, some of which were well measured and others only crudely estimated.

I defined a climate forcing as an imposed perturbation (disturbance) of the planet’s energy balance. It is measured in watts per square meter. For example, if the sun becomes 1 percent brighter, that is a forcing of about two watts (for brevity I sometimes will omit “per square meter” in discussing forcings), because Earth absorbs about 240 watts of sunlight averaged over day and night.

One large climate forcing that we know about is caused by volcanic eruptions that inject sulfur dioxide gas into Earth’s lower stratosphere (altitude ten to twenty miles). Sulfur dioxide combines with oxygen and water to form tiny sulfuric acid droplets (aerosols) that scatter sunlight back to space, reducing solar heating of Earth’s surface. Aerosols created by the 1991 eruption of Mount Pinatubo in the Philippines reduced solar heating of Earth by almost 2 percent, a negative forcing of about −4 watts. This large forcing, however, was present only briefly—after two years most of the Pinatubo aerosols had fallen out of the atmosphere. This brevity greatly reduces the effect of volcanoes on long-term climate, but an effect on the climate trend might be detectable if, say, there is an unusual concentration of volcanic eruptions in a given century.

The largest human-made climate forcing is due to greenhouse gases. These are gases that partially absorb infrared (heat) radiation, so an increased gas amount makes the atmosphere more opaque at infrared wavelengths. This increased opacity causes heat radiated to space to arise from a higher level in the atmosphere, where it is colder. Heat radiation to space is therefore reduced, resulting in a planetary energy imbalance. So Earth radiates less energy than it absorbs, causing the planet to warm up.

How much climate responds to a specified forcing—specifically, how much global temperature will change—is called “climate sensitivity.” I told the Task Force that climate sensitivity is reasonably well understood, on the basis of Earth’s history. Paleoclimate (ancient climate) records show accurately how Earth responded to climate forcings over the past several hundred thousand years.

However, because our presentations were limited to about twenty minutes each, I chose to focus on a comparison of the different climate forcing agents that drive climate change, as an effective way to show the human contribution to global warming. It is useful to simply compare the forcings, because the global temperature change is expected to depend on the size of the forcing, more or less independent of the forcing mechanism. This expectation is supported by climate model studies and empirical data (see chapter 3).

The first seven forcings in figure 1 are all human-induced. However, it’s useful to first discuss the natural forcings, changes of the sun and volcanic activity.

Changes of the sun’s irradiance (brightness seen from Earth) cause a potentially significant climate forcing on decade-to-century time scales. Unfortunately, precise measurements of solar brightness became possible only with satellite observations that began in the late 1970s. These data revealed a cyclic change of about 0.1 percent with the ten-to-twelve-year solar magnetic cycle, yielding a ten-to-twelve-year cyclic forcing of just over 0.2 watts.

The direct effect of solar brightness is amplified by at least one indirect effect. The solar variability is much larger at ultraviolet wavelengths than it is at visible wavelengths. Ultraviolet radiation breaks up oxygen molecules in Earth’s atmosphere, creating ozone, which increases the greenhouse effect. This indirect climate forcing enhances the direct solar forcing by perhaps as much as one third, making the total cyclic solar forcing about 0.3 watts.