Time's up, CO2.

![][1] CREDIT: DUNCAN.HULL/WIKIMEDIA CMMONS/CC BY-SA Forty years ago this summer, a small group of atmospheric and ocean scientists met in Woods Hole, Massachusetts, to project the future impacts on Earth's climate from atmospheric release of carbon dioxide (CO2) from fossil fuel combustion. Frank Press, head of the United States Office of Science and Technology Policy and Science Adviser to President Carter, requested that the National Academy of Sciences conduct the study for the benefit of policymakers. On the basis of then-current trends, the 1979 committee, led by Jule Charney of the Massachusetts Institute of Technology, assumed that atmospheric CO2 concentrations would reach double the preindustrial values sometime in the first half of the 21st century. They calculated that as a result, the average global surface temperature would increase by 3° ± 1.5°C, with the greatest warming at high latitudes—the first assessment of its kind. The Charney committee also noted in the models a lag on the order of decades between CO2 release and the resulting temperature rise. This delay, from disequilibrium effects with the ocean, masks pending temperature increases long before they are apparent. ![][2] Hurricane Lane devastated Hawaii in 2018. CREDIT: NASA WORLDVIEW/WIKIMEDIA COMMONS Fast-forward to 2019, and these calculations of the sensitivity of climate to a doubling of CO2 have proven to be remarkably on target. Indeed, on the basis of today's more sophisticated climate models, the Intergovernmental Panel on Climate Change confirms the climate sensitivity proffered by the Charney report. Furthermore, the lag between emission and resulting temperature increases has contributed to society's inaction on a degree of warming to which the planet is already committed from existing emissions. Four decades later, time is running out to control greenhouse gases. What else can scientists do to spur action to avert the worst impacts of climate change? Back in 1979, without insight as to what revolutions might reshape the world economy their grandchildren would inherit, or how the biosphere might create feedbacks, the Charney committee focused on what they could estimate: the radiative effect of CO2 in the atmosphere; the negative feedback from clouds; and the ability of the oceans to absorb atmospheric heat. Since then, our scientific understanding of the impacts of climate change has grown well beyond just surface temperature change, and we have deepened our knowledge about the roles of clouds, oceans, aerosols, and other non-CO2 greenhouse gases. In particular, the science of attributing changes in the frequency and severity of extreme weather events to climate change drivers has been building credibility. Whether the extreme event is a heatwave, flood, drought, wildfire, or hurricane, demonstrating to the public how climate change is amplifying the negative impacts of these events can spur more immediate action, even before the most catastrophic warming is upon us. Opinion polls reveal that a majority of Americans are worried about extreme heat, flooding, drought, or water shortages. However, even those who do view climate change as an important national issue rank it well down the list after health care, jobs, and the economy. Geoscientists must work collaboratively with health care professionals, economists, and engineers to link the changing impacts of extreme events and their aftermath to climate change while the effects are still being experienced. This approach could well convince people that climate change is about health, jobs, and the economy. The Charney report demonstrates the power of scientific prediction. Since its release, scientists have built a formidable evidence base on climate change. At no time since 1979 has the science backed down from its dire predictions for the prospects of human civilization to prosper in a world warming well beyond limits encountered in all of human history. The scientific community must better connect the issues with what now matters to the public, so that the evidence is acted upon for the benefit of society. [1]: /embed/graphic-1.gif [2]: /embed/graphic-2.gif