Energy and Climate Quotes

“Temperatures have declined more or less steadily since, interrupted by modest warming between about AD 950 and 1250 (the Medieval Optimum) followed by an interval of much colder conditions (the Little Ice Age) between about AD 1500 and 1850. The longer record of past climates and the role imputed to changes in the Earth’s orbital properties suggest that by the time of the Little Ice Age the Earth might have been well on its way to the next Big Ice Age. In this case, we humans, by adding large concentrations of CO2 to the atmosphere by burning coal, oil, and natural gas, may have saved the day. But, as we will discuss later, by this point we may have gone too far! So, to respond to those”
― Michael B McElroy, Energy and Climate: Vision for the Future

“A sharp pulse of warming was observed both in Greenland and in the tropics beginning at about 15,000 years BP. This was followed by an abrupt climate reversal, a resumption of near glacial conditions that set in at about 13,000 years BP and lasted about 2,000 years. This cold snap, referred to as the Younger Dryas, was apparently global in scale and is usually attributed to a change in the circulation of the Atlantic Ocean. It is interesting to note that the final cold-to-warm transition that marked the end of the Younger Dryas appears to have taken place over a time interval as brief as 20 years, highlighting the fact that important changes in climate can take place extremely rapidly—something”
― Michael B McElroy, Energy and Climate: Vision for the Future

“The last ice age drew to a close approximately 20,000 years BP. Sea level at that time was about 120 meters lower than it is today, reflecting the great mass of water that had been withdrawn from the ocean to supply the demand for water in the continental ice sheets. As recent as 7,000 years BP, sea level was still approximately 20 meters lower than it is today. Recovery of climate from the last ice age”
― Michael B McElroy, Energy and Climate: Vision for the Future

“Climates were relatively warm during the geological period referred to as the Cretaceous, which lasted from about 145 to about 66 million years BP. Warm conditions persisted to about 5 million years BP. The forest-tundra boundary extended at that time to latitudes as high as 82° N, some 2,500 km north of its present location, occupying regions of Greenland now permanently covered in ice. There were times when frost-tolerant vegetation was common in Spitsbergen (paleolatitude 79° N), when alligators and flying lemurs lived happily on Ellesmere Island (paleolatitude 78° N), and when palm trees, incapable of surviving even temporary frost conditions, could grow and survive in Central Asia.”
― Michael B McElroy, Energy and Climate: Vision for the Future

“Fortunately for us, the sedimentary sink is transitory. Sediments are transported on the giant crustal plates that float like rafts on the hot heavier material of the underlying mantle. When plates converge, they can be either uplifted or they may be withdrawn into the underlying mantle. Uplift results in the formation of mountain ranges. Carbon (and other life-essential elements) may be cycled directly back to the atmosphere/biosphere system, in this case by weathering of the uplifted rock material. If the sedimentary material is carried down into the mantle, it will be raised to high temperature through exposure to the hot mantle material. The carbon and other volatile materials included in the sediments may be released and transferred, often explosively, back to either the atmosphere or ocean as a component of hot springs and volcanoes. The average carbon atom has gone through this tectonically driven cycling sequence at least 10 times over the course of Earth history. How”
― Michael B McElroy, Energy and Climate: Vision for the Future

“Consider carbon, for example. The lifetime of carbon in the combined atmosphere-ocean-biosphere, the time it takes on average before the typical carbon atom is transferred to the sediment, is less than 200,000 years.”
― Michael B McElroy, Energy and Climate: Vision for the Future