NEW YORK, New York, July 26, 2015 (ENS) – Leading climate scientist and activist James Hansen is warning that the 2 degree Celsius limit to Earth’s temperature rise agreed by world leaders is “highly dangerous.” His new research paper shows that sea levels are rising much more quickly that previously believed.
An adjunct professor in the Department of Earth and Environmental Sciences at Columbia University, Dr. Hansen is lead author of a paper entitled, “Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming is highly dangerous” just published in the journal “Atmospheric Chemistry and Physics Discussion.”
The paper is published ahead of the United Nations Climate Summit set for Paris in November and December. There world leaders are expected to agree on a universal, legally-binding agreement to limit the greenhouse gas emissions responsible for global warming.
“Humanity is rapidly extracting and burning fossil fuels without full understanding of the consequences. Current assessments place emphasis on practical eﬀects such as increasing extremes of heat waves, droughts, heavy rainfall, ﬂoods, and encroaching seas,” the authors write.
“We suggest that a strategic approach relying on adaptation to such consequences is unacceptable to most of humanity, so it is important to understand this threat as soon as possible,” write Hansen and his co-authors.
They examine events late in the last interglacial period warmer than today. It is called Marine Isotope Stage (MIS) 5e in studies of ocean sediment cores, the Eemian period in European climate studies, and sometimes Sangamonian in American literature.
Accurately known changes of Earth’s astronomical conﬁguration altered the seasonal and geographical distribution of incoming radiation during the Eemian, resulting in global warming.
“While the Eemian is not an analog of future warming, it is useful for investigating climate feedbacks, the response of polar ice sheets to polar warming, and the interplay between ocean circulation and ice sheet melt,” write the authors, who add, “Our study relies on a large body of research by the scientiﬁc community.”
There is evidence of ice melt, sea level rise to nine meters (nearly 30 feet), and extreme storms in the prior interglacial period that was less than 1◦C warmer than today, the scientists write.
They say “Human-made climate forcing is stronger and more rapid than paleo forcings, but much can be learned by combining insights from paleoclimate, climate modeling, and on-going observations.”
They argue that ice sheets in contact with the ocean are vulnerable to disintegration in response to ocean warming.
They estimate that ice sheet mass loss can be approximated by a doubling time up to sea level rise of at least several meters. “Doubling times of 10, 20 or 40 years yield sea level rise of several meters in 50, 100 or 200 years,” the scientists warn.
They consider paleoclimate data showing that subsurface ocean warming causes ice shelf melt and ice sheet discharge.
“Our climate model exposes amplifying feedbacks in the Southern Ocean that slow Antarctic bottom water formation and increase ocean temperature near ice shelf grounding lines, while cooling the surface ocean and increasing sea ice cover and water column stability,” write Hansen and his colleagues.
Despite these warnings, global carbon dioxide emissions continue to increase as fossil fuels remain the primary energy source.
They point to the argument made by fossil fuel proponents that it is economically and morally responsible to continue fossil fuel use for the sake of raising living standards, with expectation that humanity can adapt to climate change and ﬁnd ways to minimize effects via advanced technologies.
“We suggest that this viewpoint fails to appreciate the nature of the threat posed by ice sheet instability and sea level rise,” the scientists write.
“If the ocean continues to accumulate heat and increase melting of marine-terminating ice shelves of Antarctica and Greenland, a point will be reached at which it is impossible to avoid large scale ice sheet disintegration with sea level rise of at least several meters,” they warn.
Hansen and his co-authors conclude, “The economic and social cost of losing functionality of all coastal cities is practically incalculable.”