in the trenches/climate
11. Real Time
Yes, Virginia, 1997 was the hottest year on record!
It was a close race, as our graphics demonstrate, but all three of the most reliable data sets agreed: the Hadley Centre of the British Meteorological Office, the U.S. National Oceanic and Atmospheric Administration (NOAA), and the Goddard Institute for Space Studies (GISS), which provided our figures, affirmed that 1997 beat out 1995 and 1990 as the warmest year ever, since detailed temperature records began more than a hundred years ago.
According to NOAA, 1997's global average temperature was 62.45 degrees Fahrenheit -- three-quarters of a degree above the "normal" average for the past 30 years, and 0.15 degrees above the previous high, set in 1990. GISS data found that 1997 exceeded the previous record year by an even smaller amount -- only about two hundredths of a degree F.
Though just a few months ago, it seemed unlikely that 1997 would come out on top, this did indeed occur, as our monthly temperature chart reveals, because of a very mild period from October through December, including extremely warm ocean temperatures, the result of a powerful El Nino. Nevertheless, as noted in January's New in the Literature, "even without El Nino, 1997 would have been a very warm year,'' according to Tom Karl of NOAA, who also pointed out that nine of the hottest years on record have all occurred in the last eleven years, and the warmest five since 1990.
It was this string of exceptionally torrid years over the last decade, rather than the record-breaking status of 1997 that enabled NOAA scientists for the first time to announce that the warming climate is the result, at least in part, of the accumulation of human-caused greenhouse gases in the atmosphere.
More comments, excerpted from a statement of James Hansen, noted climatologist and director of GISS, follow:
"Global surface air temperature in 1997 was warmer than any previous year this century, marginally exceeding the temperature of 1995. The 1990s are significantly warmer than any previous decade in the period of instrumental data, with the four warmest years of the century being 1990, 1991, 1995 and 1997. Regionally, the eastern part of the United States was cooler than normal in 1997..."
"In most years the land-based and the land plus ocean analyses are in close agreement. However, they differ noticeably in 1997 because of the unusually high temperatures in the tropical Pacific Ocean associated with one of the strongest El Ninos on record. In the land-based analysis 1997 is the fourth warmest year in the record. In the land-ocean temperature index 1997 is the warmest year, being slightly (about 0.01C) warmer than 1995."
Hansen, who just last spring predicted that one of the next three years would set a new global temperature record, is now anticipating that over the next couple of years, the record will be broken by a much larger amount as a result of on-going climate change, by about two tenths of a degree F.
Thanks for keeping track of 1997 temperatures with us. Would you like Liberty Tree to continue this process for 1998? All votes will be duly counted; any suggestions for making the process more intelligible or compelling would also be appreciated. Let us know what you think: listen@libtree.org
ANNUAL AVERAGE GLOBAL TEMPERATURE
(Centigrade)
Jan-Feb 1998 14.66
MONTHLY AVERAGE GLOBAL TEMPERATURE
(Centigrade)
NOTES:
Annual Average Global Temperature -- this table compares 1997's annual average global temperature to date (currently: January thru December 1997) with the global average annual temperature for our benchmark years.
Monthly Average Global Temperature -- this graph compares the 1997's monthly global average temperatures with the same measure for our benchmark years. These figures are used to compute the data expressed in the Annual Average Global Temperature table.
Baseline Period (1951-1980): the baseline cumulative global average temperature we are using for this benchmark period is 14 C. All other temperature data (including single years within the baseline period) are calculated relative to the baseline period global average temperature. In other words, the temperature data you see here do not indicate absolute temperature changes, but deviations of the temperature from the "normal" temperature for that period. Normal, in this case, being defined as the "average over the 30 years from 1951 to 1980."
(Please note that 14C is a rough estimate for the cumulative global average temperature. According to a GISS scientist, the 14 C measurement is an arbitrary number, a rough estimate for the global temperature. The curves on our graphs would look exactly the same if a different number were used (zero, for example) since changing the basline number would move the entire curve up or down along the verical axis of the graph, it would not change the position of the individually plotted points on the curve relative to one another. What is important here, and what we are trying to illustrate, is the deviation of the temperature from a historically based "normal" temperature.)
1972: a random year within the baseline period selected for comparison.
1995: globally, the hottest year on record, before 1997.
This data provided courtesy of NASA's Goddard Institute for Space Studies (GISS). The temperatures used as data for these graphs are from Goddard's land-ocean temperature index. That index is based on temperature measurements taken at the surface of the land and oceans. There are other ways to measure temperature (via satellite or balloons, for example) and these other methods may not yield the same results.
Get more information about how this data is calculated.
More on Climate:
Table of Contents | Twelve Hundred Words or Less... | Web Resources
Activist Groups | Voices | New in the Literature | Hotspots
History of Climate Negotiations | Glossary of Negotiator Terms | On the Other Hand...
Policy Options | Technological Breakthroughs? | Want to Get Involved?
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