Ed Landing

Climatologists, like Walter Broecker and James Hansen , have predicted a warmer climate due to the accumulation of greenhouse gasses in the atmosphere from the burning of fossil fuels. Geologists take a longer view. On a geological timescale, it appears that the Earth has long oscillated between "greenhouse" and "ice house" conditions. During greenhouse periods, the average global temperature has been a balmy 22°C (72°F), quite a bit warmer than the 2012 average of about 14.4°C, one of the hottest years that climatologists have actually recorded. But all of man's time on Earth has so far been spent within a few degrees of ice house conditions. Greenhouse conditions of the geologic past were warm enough to melt all the world's glaciers and icecaps, causing a sea level rise of about 100 meters. However, global sea level rise may have been more than twice that during the Cambrian and the Ordovician periods. Ed Landing, New York State Paleontologist and Curator of Paleontology, New York State Museum, has a theory to explain the extra water rise: global hyperwarming. According to Landing, hyperwarming is a feedback effect as shallow seas overlap the continents. Shallow seas absorb sunlight and warm, and will also cause the world ocean to become warmer; there is also an increase in atmospheric water vapor with greater evaporation from the shallow seas and ocean. Water vapor is itself a potent greenhouse gas, causing yet more heating. The extremely high sea levels come about because of thermal expansion of the world ocean --a phenomenon already being detected as a result of modern anthropogenic warming. Some of the evidence that Landing sees for hyperwarming are the layers of black shale and slate laid down over North America, which formed from thick anoxic, carbon rich mud on the bottom of those ancient shallow seas and on lower parts of the ancient continental slopes. Very high temperatures reduce oxygen solubility and allow expansion of low oxygen water into near shore environments. AAAS Members Central: The first scary notion is the idea that greenhouse conditions are the default state of the planet. So, is it true that the Earth was headed for very much warmer temperatures on a geological time scale, anyway, but we are vastly accelerating the process? Ed Landing, New York State Paleontologist and Curator of Paleontology, New York State Museum: Greenhouse conditions reflect the continued input of carbon dioxide ultimately from sources in Earth's mantle. The carbon dioxide is then brought to the surface with volcanism at spreading centers. The new carbon dioxide is then taken out of the system by reef production of calcium carbonate (lime), by sequestering by land plants (from peat to coal) and marine phytophankton (which are eaten by planktivores), and the oily fecal debris sinks to the sea floor and, if not oxidized, accumulated as petroleum source rocks. The typical alternative is "ice house conditions," which appear with global cooling typically brought about as a major continent enters high or polar latitudes and undergoes a period of continental glaciation (as present Antarctica), or the circulation of warm water into a polar sea (the Arctic Ocean) becomes reduced as plate tectonics brings land masses into the polar area to isolate the polar sea and reduce the amount of warm water brought to the pole (north or south) and cause it to cool and likely develop pack ice. Both continental glaciers and pack ice increase albedo and cause cooling by reflecting heat to space. The recent James Hansen/Al Gore/Bill McKibben synthesis is that the steady accumulation of carbon dioxide since about 1850 will "artificially" take Earth out of its 2.6 million year ice house condition and lead to a greenhouse world. The amount of carbon dioxide now in the atmosphere is the greatest it has been for more than 400,000 years (based on ice cores). Accelerated atmospheric and ocean warming will begin (initially subtly) with the rise of sea-level