Climate: Long range Investigation, Mapping, and Prediction
Encyclopedia
Map
A map is a visual representation of an area—a symbolic depiction highlighting relationships between elements of that space such as objects, regions, and themes....
of climate
Climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
conditions during the last glacial maximum
Last Glacial Maximum
The Last Glacial Maximum refers to a period in the Earth's climate history when ice sheets were at their maximum extension, between 26,500 and 19,000–20,000 years ago, marking the peak of the last glacial period. During this time, vast ice sheets covered much of North America, northern Europe and...
. The project was funded by the National Science Foundation
National Science Foundation
The National Science Foundation is a United States government agency that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National Institutes of Health...
as part of the International Decade of Ocean Exploration (1970s) and is based in large part of the collection and analysis of a very large number of sediment cores to create a snapshot of conditions across the ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
s. The CLIMAP project also resulted in maps of vegetative zones across the continents and the estimated extent of glaciation at the time. Most CLIMAP results aim to describe the Earth as it was 18 thousand years ago, but there was also an analysis to look at conditions during the previous interglacial
Interglacial
An Interglacial period is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age...
—120 thousand years ago (CLIMAP 1981).
CLIMAP has been a cornerstone of paleoclimate research and remains the most used sea surface temperature reconstruction of the global ocean during the last glacial maximum (Yin and Battisti 2001), but it has also been persistently controversial. CLIMAP resulted in estimates of global cooling of only 3.0 ± 0.6°C relative to the modern day (Hoffert and Covey 1992). The climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
during an ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
that occurs far from the continental ice sheet
Ice sheet
An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² , thus also known as continental glacier...
s themselves is believed to be primarily controlled by changes in greenhouse gas
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...
es, hence the conditions during the last glacial maximum provide a natural experiment for measuring the impact of changes in greenhouse gases on climate. The cited estimates of 3.0 °C implies a climate sensitivity to carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
changes at the low end of the range proposed by the Intergovernmental Panel on Climate Change
Intergovernmental Panel on Climate Change
The Intergovernmental Panel on Climate Change is a scientific intergovernmental body which provides comprehensive assessments of current scientific, technical and socio-economic information worldwide about the risk of climate change caused by human activity, its potential environmental and...
http://www.grida.no/climate/ipcc_tar/wg1/325.htm.
However, CLIMAP also suggested that some of the tropics
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
and in particular much of the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
were warmer than they are today. To date, no climate model
Climate model
Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. They are used for a variety of purposes from study of the dynamics of the climate system to projections of future climate...
has been able to reproduce the proposed warming in the Pacific (Yin and Battisti 2001), with most preferring a several degree cooling. Also, it appears that climate models which are forced to match the CLIMAP sea surface measurements are too warm to match estimates for changes at continental locations (Pinot et al. 1999). These factors suggest that CLIMAP systematically overestimated the temperatures in the tropical oceans during the last glacial though there is at present no consistent explanation for why or how this should have happened. Unfortunately cost and difficulty of collecting sediment cores from the open Pacific has limited the availability of samples that might help to confirm or disprove these observations. If the Pacific reconstruction is assumed to be in error, it would result in a larger climate sensitivity to changes in greenhouse gases.