In 1988, NASA climate scientist James Hansen testified before the U.S. Senate Energy and Natural Resources Committee that humanity was the cause of greenhouse gases that were transforming the climate and threatening civilization. Last week, Dr. Hansen and 16 colleagues released a report documenting a more rapid change in climate than previously anticipated. Earth is already nearing average temperatures that are more than 1.5°C or 2.7°F higher than preindustrial norms. Dr. Hansen, director at the Earth Institute at Columbia University, called the projected 1.5-degree tipping point that activists hoped to avoid “deader than a doornail . . . In the next several months, we’re going to go well above 1.5C on a 12-month average.” The United Nations Intergovernmental Panel on Climate Change warns that there will be severe and potentially irreversible consequences above that level. Staple crops will wither and water sources will dry up. Record temperatures this summer were 1.5 to 1.6 degrees hotter than the preindustrial average. Hansen’s team predicts that the 1.5°C benchmark will be passed this decade and 2°C will be passed before 2050.
The data on climate change is more precise than in the past, but it is not new. Since the end of World War II, scientists have greatly expanded our understanding of the impact of the Industrial Revolution and greenhouse gas emissions on climate. They include discoveries about the limited capacity of the Earth’s oceans to absorb CO2 and the accumulation of CO2 in the atmosphere. In a May 1965 speech, Dr. Philip Abelson, editor of the journal Science, explained how humanity had already altered the Earth’s climate by introducing excess carbon dioxide and other greenhouse gases into the atmosphere, which contributed to a general warming trend from 1900 to 1950. In November 1965, the Environmental Pollution Panel of the President’s Science Advisory Committee issued a report on climate change that included a section on atmospheric carbon dioxide concentrations. The report presented the scientific conclusion that “with fair assurance that at the present time, fossil fuels are the only source of CO2 being added to the ocean-atmosphere-biosphere system.” The report warned that by 2000 climate change could lead to melting ice caps, rising sea levels, and ocean acidity and in 1975, Wallace Broecker, a geochemist at Columbia University, accurately predicted the level of global warming that would impact the Earth’s climate by 2015.
Five years later, in 1979, the National Academy of Sciences (NAS) established an Ad Hoc Study Group on Carbon Dioxide and Climate headed by meteorologist Jule Charney of the Massachusetts Institute of Technology. The NAS committee’s report declared, “we now have incontrovertible evidence that the atmosphere is indeed changing and that we ourselves contribute to that change. Atmospheric concentrations of carbon dioxide are steadily increasing, and these changes are linked with man’s use of fossil fuels and exploitation of the land” (vii). The study group issued a dire warning, “we have tried but have been unable to find any overlooked or underestimated physical effects that could reduce the currently estimated global warmings due to a doubling of atmospheric CO2 to negligible proportions or reverse them altogether. However, we believe it quite possible that the capacity of the intermediate waters of the oceans to absorb heat could delay the estimated warming by several decades. It appears that the warming will eventually occur, and the associated regional climatic changes so important to the assessment of socioeconomic consequences may well be significant, but unfortunately the latter cannot yet be adequately projected” (3). The study group believed its conclusions would be “comforting to scientists,” but they would be “disturbing to policymakers” (viii).
In 1988, the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) created the Intergovernmental Panel on Climate Change (IPCC) to study the physical science of climate change and the numerous effects of the changes. The First Assessment Report (FAR) in 1990 stated, “emissions resulting from human activities are substantially increasing the atmospheric concentrations of the greenhouse gases.” Since then, the dangers have only grown closer and clearer with each report. New reports not only forecast hazards but describe the present chaos too. As the 2018 Special Report (SR15) explained, “we are already seeing the consequences of 1°C of global warming through more extreme weather, rising sea levels and diminishing Arctic sea ice, among other changes.”
In January 2019, teenage climate activist Greta Thunberg, insisted in a speech at the World Economic Forum in Davos, Switzerland that “Our House is on Fire.” Thunberg warned that according to the Intergovernmental Panel on Climate Change, humanity was less than 12 years away from a tipping point where it would no longer be able to undo ecological mistakes. There are at most eight years left.
Testimony by Dr. James Hansen, Director, NASA Goddard Institute for Space Studies
U.S. Senate Committee on Energy and Natural Resources, June 23, 1988
“I would like to draw three main conclusions. Number one, the earth is warmer in 1988 than at any time in the history of instrumental measurements. Number two, the global warming is now large enough that we can ascribe with a high degree of confidence a cause and effect relationship to the greenhouse effect. And number three, our computer climate simulations indicate that the greenhouse effect is already large enough to begin to affect the probability of extreme events such as summer heat waves . . . The present temperature is the highest in the period of record. The rate of warming in the past 25 years . . . is the highest on record. The four warmest years . . . have all been in the 1980s. And 1988 so far is so much warmer than 1987, that barring a remarkable and improbable cooling, 1988 will be the warmest year on the record.”
“Causal association requires first that the warming be larger than natural climate variability and, second, that the magnitude and nature of the warming be consistent with the greenhouse mechanism . . . The observed warming during the past 30 years . . . is almost 0.4 degrees Centigrade by 1987 relative to climatology, which is defined as the 30 year mean, 1950 to 1980 and, in fact, the warming is more than 0.4 degrees Centigrade in 1988. The probability of a chance warming of that magnitude is about 1 percent. So, with 99 percent confidence we can state that the warming during this time period is a real warming trend . . . Altogether the evidence that the earth is warming by an amount which is too large to be a chance fluctuation and the similarity of the warming to that expected from the greenhouse effect represents a very strong case. In my opinion, that the greenhouse effect has been detected, and it is changing our climate now.”
“I would like to address the question of whether the greenhouse effect is already large enough to affect the probability of extreme events, such as summer heat waves . . . [W]e have used the temperature changes computed in our global climate model to estimate the impact of the greenhouse effect on the frequency of hot summers in Washington, D.C. and Omaha, Nebraska. A hot summer is defined as the hottest one-third of the summers in the 1950 to 1980 period, which is the period the Weather Bureau uses for defining climatology. So, in that period the probability of having a hot summer was 33 percent, but by the 1990s, you can see that the greenhouse effect has increased the probability of a hot summer to somewhere between 55 and 70 percent in Washington according to our climate model simulations . . . [I]n the late 1980’s and in the 1990’s we notice a clear tendency in our model for greater than average warming in the southeast United States and the midwest. In our model this result seems to arise because the Atlantic Ocean off the coast of the United States warms more slowly than the land. This leads to high pressure along the east coast and circulation of warm air north into the midwest or the southeast. There is only a tendency for this phenomenon. It is certainly an imperfect tool at this time. However, we conclude that there is evidence that the greenhouse effect increases the likelihood of heat wave drought situations in the southeast and midwest United States even though we cannot blame a specific drought on the greenhouse effect.”