Is the world actually getting warmer?
If it is, what is causing this warming?
Is a warmer globe necessarily a bad thing?
How is a global temperature measured?
Historical records are also used - municiple/state/federal records, amatuer records, diaries.
Limited span of time for which these record can be used.
Proxy records are data from sources which do not give actual temperatures but provide information which can be used to infer the temperature.
Biologic, geologic, and chemical sources can be used.
Biological Proxy Records - tree rings, pollen, floral and faunal distributions
Geological Proxy Records - sediment deposits, minerals, geochemistry, glacial deposits
Chemical Proxy Records - O18/O16 ratios
In order to properly study the question of global warming, the length of time being studied must be considered. A trend over the short period may show an increase or decrease while the longer period may show the same trend, or opposite trend.
Temperature: 1600 to 1985.
(Image modified from: Bradley, 1985)
Temperature: 1860 to 1985.
(Image modified from: Gribbin, 1990)
Temperature: 1880 to 2006.
(Data from Global Surface Temperature Anomalies, National Climatic Data Center, 6 February 2006. Anomalies are provided as departures from the 20th century average (1901-2000). http://www.ncdc.noaa.gov)
Sea Level: 1880 to 1980.
(Image modified from: Gribbin, 1990)
Moline Airport Temperature: 1943 to 1993.
(Data for Moline Airport obtained from the National Climatic Data Center)
Estimated Sea Surface Temperature: 130,000 BP to Present.
(Image modified from: Bradley, 1985)
Graph based on foram fossil record (sea organisms that are sensitive to ocean surface temperature).
BP = years Before Present
Note the increase in temperature beginning ~18,000 years ago.
Note that temperature 120,000 years ago was warmer than today.
Temperature and CO2: 165,000 BP to Present.
(Image modified from: Schneider, 1989)
Temperature and Carbon Dioxide content of the atmosphere obtained from air bubbles trapped in ancient polar ice sheets from Antarctica.
Note the similarity with foram temperature record.
The correlation between the carbon dioxide record and temperature record.
Mean Global Temperature: 4.6 b.y. to Present.
(Image modified from: Bradley, R.S., 1985)
b.y. = billion years
Data for this graph is dased on many different types of geological, biological and chemical proxy records for the entire history of the Earth.
Temperature is given as either warmer or cooler than present.
Milankovitch Cycles
Based on variations in the orbital parameters of the Earth and Earth's axis.
1) Axial tilt
2) Precession
3) Orbital Eccentricity
comnination of these factors results in periods of time when the Earth receives either greater or lesser amounts of solar radiation.
Insolation: 1,000,000 BP to Present.
(Data from Berger A. and Loutre M.F., 1991, Insolation values for the climate of the last 10 million years. Quaternary Sciences Review, Vol. 10 No. 4, pp. 297-317, 1991. http://www.ncdc.noaa.gov/paleo/forcing.html)
Atmospheric Carbon Dioxide: 100,000 BP to Present.
(Data from Petit, J.R., et al., 2001, Vostok Ice Core Data for 420,000 Years, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2001-076. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. http://www.ncdc.noaa.gov/paleo/forcing.html)
Atmospheric Carbon Dioxide: 1958 to 2006.
(Data from March 1958 to April 1974 are from the Scripps Institution of Oceanography (SIO) and where obtained from the Carbon Dioxide Information Analysis Center (CDIAC). Source: http://www.ncdc.noaa.gov/paleo/trends.html)
Annual Carbon Dioxide Emissions: 1850 to 2000.
(Graph from Woods Hole Research Center's "Understanding the Global Carbon Cycle" by Richard Houghton. Source: http://www.whrc.org/carbon/index.htm)
The unit on the graph PgC is Petagrams of Carbon. 1 Petagram = 1 x 1015 grams = 1 billion metric tons
Atmospheric Methane: 100,000 BP to Present.
(Graph from Petit, J.R., et al., 2001, Vostok Ice Core Data for 420,000 Years, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2001-076. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. http://www.ncdc.noaa.gov/paleo/forcing.html)
Atmospheric Methane: 1986 to 2006.
(Graph from NOAA ESRL Global Monitoring Division's "Observatory Measurements". Source: http://www.cmdl.noaa.gov/ccgg/insitu.html)
Is the world actually getting warmer?
If it is, what is causing this warming?
Is a warmer globe necessarily a bad thing?
Additional Reading in This Topic
