Unit ObjectivesUnit Objectives
Preparation for Online and Class
Discussion
 | Global tropospheric temperatures as measured by the Microwave Sounding Units (MSU) |
| From NOAA: Annual Review of 1998 Climate. |
| The Global Historical Climatology Network (GHCN) |
| From NOAA: Drought history and predictions |
| El Niņo and global warming: What's the connection? |
| Natural climate variability vs. man-made climate change. From UNEP. |
| Precipitation increase over the US in the 20th Century |
| Will climate change lead to more extremes and disasters? From UNEP. |
| Houghton, J. T., L. G. Meira Filho, B. A. Callander N. Harris, A. Kattenberg, and K. Maskell, 1996: Climate Change 1995. The Science of Climate Change. Cambridge University Press, 423-434. |
| Houghton, J. T., G. J. Jenkins, and J. J. Ephraums, 1990: Climate Change, The IPCC Scientific Assessment. Cambridge University Press. p. 216-223. |
Online and Class Discussion
Unit Wrap-up MaterialsSummary prepared by: Group 9Trends in Climate Variables, Climate Variability, Global Warming Update Global surface temperatures have increased about 0.6°C (plus or minus 0.2°C) since the late-19th century, and about one half degree F (0.2 to 0.3°C) over the past 25 years. Although there is a warming trend some areas (including parts of the southeastern U.S.) have actually cooled. The recent warmth has been greatest over N. America and Eurasia between 40 and 70°N. An enhanced greenhouse effect is expected to cause cooling in higher parts of the atmosphere because the increased "blanketing" effect in the lower atmosphere traps heat. Cooling of the lower stratosphere (about 30-35,000ft.) since 1979 is shown by both satellite Microwave Sounding Unit and radiosonde data. Cloud cover has increased in many of the areas with reduced diurnal temperature range. Relatively cool surface and tropospheric temperatures, and a relatively warmer lower stratosphere, were observed in 1992 and 1993, following the 1991 eruption of Mt. Pinatubo, the warming reappeared in 1994. A dramatic global warming, at least partly associated with the record El Niņo, took place in 1998. This warming episode is reflected from the surface to the top of the troposphere. El Niņos are not caused by global warming but there is clear evidence exists from a variety of sources. El Niņos have been present for hundreds, and some indicators suggest maybe millions, of years. It has been suggested that warmer global sea surface temperatures can enhance the El Niņo phenomenon, it has also been found that El Niņos have been more frequent and intense in recent decades.
On a global scale there is little evidence of sustained trends in climate variability or extremes. This could be due to inadequate data analyses. On regional scales there is evidence of changes in variability and/or extremes. In the United States alone over 200 tornadoes were observed in January 1999, nearly 14 times the average number in addition to that the annual record for 1999 also contained five category 4 hurricanes, the greatest number in any one year on record. Some areas have shown evidence of increases in the intensity of extreme rainfall events, but no clear global pattern has emerged. Global mean sea level has been rising at a significantly larger rate, 1 to 2mm/year, than that of the past 100 years. Increase for the 21st century is thought to be about 0.5 meter, but estimates range.
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Trends in global average surface temperature
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Precipitation changes: trend over land from 1900 to 1994 |
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Sea level rise due to global warming
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The great weather and flood catastrophes
over the last forty years |
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Thinning of the Artic
sea-ice |
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Evolution of the ice-breaking date
in the River Tornio (Finland) |
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Changes in permafrost temperatures
at various depths in Fairbanks (Alaska) |
| A Common Sense Climate Index: Is Climate Changing Noticeably? |
| Correction to satellite based temperature record changes cooling trend to a warming trend. |
| Fact Sheet: The State of Knowledge on Global Climate Change, 1996. |
| Global Warming: Not whether it is happening but what to do about it. |
| Global Warming Measurements from Subsurface Temperatures |
| Science and Impacts of Global Warming. |
| Trends in US Extreme Weather Events |
 | Thawing Permafrost May Speed Global Warming |
| Warmer World Intensifies Extreme Weather, 'Natural' Disasters |
| Excess Heat in the Ocean |
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Global Change Course Earthreview - Links on the current state of the planet.
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| Global Climate Change Issues Forum |
| Climactic / Meteorologic Information Sources. Center for Global & Regional Environmental Research, University of Iowa. |
| Experimental Climate Prediction Center, Scripps Institution of Oceanography, University of California-San Diego. |
| Is Warming Trend Harming Penguins? |
| The sea ice in the Arctic is melting, is this a sign of global warming? |
| VEMAP Animations |
| World Climate data - average monthly and yearly rainfall, temperature, and pressure for over 85,000 sites worldwide. |
| Strum, M., C.
Racine, and K. Tape, 2001: Increasing shrub abundance in the Arctic.
Nature 411, 546-547. |
| Easterling,
D. R., T. R. Karl, K. P. Gallo, D. A. Robinson, K. E. Trenberth, and A. Dai,
2000: Observed climate variability and change of relevance to the biosphere.
J. Geophys. Res. 105,
101-120, 114. |
| American
Geophysical Union, 1999: Climate change and greenhouse gases. ESO 80,
457-458. |
| Wigley, T. M. L., R. L. Smith, and B. D. Santer, 1998: Anthropogenic influence on the autocorrelation structure of hemispheric-mean temperatures. Science 282, 1676-1679. |