Global WarmingGlobal Warming

Fact and FictionFact and Fiction

Some Critical FindingsSome Critical Findings

Global temperatures have increased Global temperatures have increased 0.6 0.6 00C the past 100 yearsC the past 100 years

In some areas, like the southeast In some areas, like the southeast United States, there has been a United States, there has been a decrease in temperatures since the decrease in temperatures since the late 19late 19thth century century

There has been a cooling of the lower There has been a cooling of the lower stratosphere which is due to the stratosphere which is due to the trapping of greenhouse gases in the trapping of greenhouse gases in the upper troposphere upper troposphere

Layers of the atmosphereLayers of the atmosphere

Stratosphere Evidence of CoolingStratosphere Evidence of Cooling

Source: http://www.ncdc.noaa.gov/oa/climate/globtemp.html

Some Critical Findings Some Critical Findings

Pre-Industrial Revolution Carbon Pre-Industrial Revolution Carbon dioxide levels were 280 ppm (.012%) dioxide levels were 280 ppm (.012%) COCO22 in the atmosphere in the atmosphere

Today the level is 388 ppm, which Today the level is 388 ppm, which demonstrates a rapid increase which demonstrates a rapid increase which has not been seen for at least has not been seen for at least 420,000 years ago. 420,000 years ago.

Increase in carbon dioxide levels between 1960 and 1990. Image from Purves et al., Increase in carbon dioxide levels between 1960 and 1990. Image from Purves et al., Life: The Science of BiologyLife: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and , 4th Edition, by Sinauer Associates (www.sinauer.com) and

WH Freeman (www.whfreeman.com).WH Freeman (www.whfreeman.com).

Past EvidencePast Evidence

Measurements from this period have Measurements from this period have been made on air trapped in ice been made on air trapped in ice cores, drilled mainly from the cores, drilled mainly from the Antarctic and Arctic, which have Antarctic and Arctic, which have extended back as far as 160,000 extended back as far as 160,000 years with the "Vostok" ice core years with the "Vostok" ice core (Gray, 1998). (Gray, 1998).

Extinctions(1)end Ordovician. (2)late Devonian. (3)end Permian. (4)end Triassic. (5)end Cretaceous

Are Ice Cores Accurate?Are Ice Cores Accurate? It is difficult to believe that a chemically It is difficult to believe that a chemically

active gas such as carbon dioxide can active gas such as carbon dioxide can remain unaffected by burial in ice for as remain unaffected by burial in ice for as long as 160,000 years. There are long as 160,000 years. There are questions whether the carbon dioxide can questions whether the carbon dioxide can diffuse through the snow, react with dust diffuse through the snow, react with dust particles, or form clathrate compounds particles, or form clathrate compounds under pressure The technique of drilling, under pressure The technique of drilling, removal and preservation of the ice core is removal and preservation of the ice core is very difficult, and there are many things very difficult, and there are many things that can go wrong (Jaworski, 1996, 1997). that can go wrong (Jaworski, 1996, 1997).

Are Ice Core Samples Accurate?Are Ice Core Samples Accurate?

Most of these objections have now Most of these objections have now been overcome, with a recent study been overcome, with a recent study on the Law Dome ice cores by on the Law Dome ice cores by Etheridge et al Etheridge et al (1996, 1998)(1996, 1998). .

Indirect EvidenceIndirect Evidence Indirect indicators of warming such as Indirect indicators of warming such as

borehole temperatures, snow cover, and borehole temperatures, snow cover, and glacier recession data, are in substantial glacier recession data, are in substantial agreement with the more direct indicators agreement with the more direct indicators of recent warmth. of recent warmth.

Large-scale measurements of sea-ice have Large-scale measurements of sea-ice have only been possible since the satellite era, only been possible since the satellite era, but through looking at a number of but through looking at a number of different satellite estimates, it has been different satellite estimates, it has been determined that Arctic sea ice has determined that Arctic sea ice has decreased between 1973 and 1996 at a decreased between 1973 and 1996 at a rate of -2.8 +/- 0.3%/decade rate of -2.8 +/- 0.3%/decade

Twenty glacier length records from different parts of the world all show a decline in lengths through the World Glacier Monitoring Program

FindingsFindings The period since 1972, when the The period since 1972, when the

increase has been linear despite an increase has been linear despite an increase of over 45% in emissions, increase of over 45% in emissions, suggests that there are new carbon suggests that there are new carbon sinks being established in the ocean sinks being established in the ocean and in the terrestrial biosphere to and in the terrestrial biosphere to absorb the increases (Gray, 1998). absorb the increases (Gray, 1998).

El NinoEl Nino

El Niños are not caused by global El Niños are not caused by global warming. warming.

However, it has been hypothesized However, it has been hypothesized that warmer global sea surface that warmer global sea surface temperatures can enhance the El temperatures can enhance the El Niño phenomenon, and it is also true Niño phenomenon, and it is also true that El Niños have been more that El Niños have been more frequent and intense in recent frequent and intense in recent decades. decades.

Sea Level RiseSea Level Rise

Global mean sea level has been Global mean sea level has been rising at an average rate of 1 to 2 rising at an average rate of 1 to 2 mm/year over the past 100 years, mm/year over the past 100 years, which is significantly larger than the which is significantly larger than the rate averaged over the last several rate averaged over the last several thousand years. Projected increase thousand years. Projected increase from 1990-2100 is anywhere from from 1990-2100 is anywhere from 0.09-0.88 meters (depending on the 0.09-0.88 meters (depending on the severity of the warming) severity of the warming)

Ocean Currents?Ocean Currents?

Illustration by Jack Cook, Woods Hole Oceanographic Institution

The FutureThe Future Due to the enormous complexity of Due to the enormous complexity of

the atmosphere, the most useful the atmosphere, the most useful tools for gauging future changes are tools for gauging future changes are 'climate models'. 'climate models'.

The Intergovernmental Panel on The Intergovernmental Panel on Climate Change (IPCC), was Climate Change (IPCC), was established to study global changeestablished to study global change

IPCC projects a global temperature IPCC projects a global temperature increase of anywhere from 1.4 - increase of anywhere from 1.4 - 5.8°C from 1990-2100 (based upon 5.8°C from 1990-2100 (based upon region of the world). region of the world).

The Future (continued)The Future (continued) Precipitation is also expected to Precipitation is also expected to

increase over the 21st century, increase over the 21st century, particularly at northern mid-high particularly at northern mid-high latitudes, though the trends may be latitudes, though the trends may be more variable in the tropics.more variable in the tropics.

Snow extent and sea-ice are also projected to decrease further in the northern hemisphere, and glaciers and ice-caps are expected to continue to retreat.

ReferencesReferences

Etheridges, D.M., L.P. Steele, R.L. Langenfelds, R.J. Francey, J.-M Barnola, V.I. Etheridges, D.M., L.P. Steele, R.L. Langenfelds, R.J. Francey, J.-M Barnola, V.I. Morgan. 1996. "Natural and anthropogenic changes in atmospheric CO2 Morgan. 1996. "Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn" J. Geophys. Res. over the last 1000 years from air in Antarctic ice and firn" J. Geophys. Res. 101 (D2) 4115-4128101 (D2) 4115-4128

Etheridges, D.M., L.P. Steele, R.L. Langenfelds, R.J. Francey, J.-M Etheridges, D.M., L.P. Steele, R.L. Langenfelds, R.J. Francey, J.-M Barnola, V.I. Morgan. 1996. "Natural and anthropogenic changes Barnola, V.I. Morgan. 1996. "Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn" J. Geophys. Res. 101 (D2) 4115-4128ice and firn" J. Geophys. Res. 101 (D2) 4115-4128

Gray, V.R., 1998. "The IPCC future projections: are they plausible" Climate Gray, V.R., 1998. "The IPCC future projections: are they plausible" Climate Research 10 155-162Research 10 155-162

http://palaeo.gly.bris.ac.uk/Palaeofiles/Permian/PALIntro.htmlhttp://palaeo.gly.bris.ac.uk/Palaeofiles/Permian/PALIntro.html

http://www.ncdc.noaa.gov/oa/climate/globalwarming.html#Q11http://www.ncdc.noaa.gov/oa/climate/globalwarming.html#Q11

Jaworowski, Z. 1996 "Reliability of Ice Core Records for Climatic Projections" in Jaworowski, Z. 1996 "Reliability of Ice Core Records for Climatic Projections" in "The Global Warming Debate", (John Emsley, Ed.) European Science and "The Global Warming Debate", (John Emsley, Ed.) European Science and Environment Forum , London, 95-105.Environment Forum , London, 95-105.

Jaworowski, Z., 1997. "Ice Core Data Show No Carbon Dioxide Increase" 21st Jaworowski, Z., 1997. "Ice Core Data Show No Carbon Dioxide Increase" 21st Century Science and Technology 10 , (1) 42-52Century Science and Technology 10 , (1) 42-52