05-19-2008, 11:08 PM
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#36 (permalink)
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| earthling
Member Since: Apr 2008 Location: L-town
Posts: 151
| Quote:
Originally Posted by AK-74me  Not time but here is a Newsweek scan that I saved a while back. | The article is mostly concerned about changing climate affecting agriculture. The gist is "earth's weather patterns have changed" which may result in a "drastic decline in food production...In England, farmers have seen their growing season decline..." but "During the same time, the average temperature around the equator has risen..." One would expect that our understanding of the factors in the planet's climate and how they interact would have increased by some extent since then. The argument now is "it's so complicated no one knows" but there has been a strong focus, especially in the last 20 years, and the climate models are much more complex than they used to be. The data from 1968 may not have been sampled well. Maybe they didn't account for global warming changing ocean currents -- maybe the Gulf Stream no longer boosted England's average temps (and growing season). It's a short article about a complicated process in a weekly newsmagazine.
The article is from 35 years ago (that's 1973 for you Wiki-morons) and it appears that the majority opinion is from NOAA reaearchers. Looking at NOAA's website today (http://lwf.ncdc.noaa.gov/oa/climate/...warming.html):
"Global surface temperatures have increased about 0.74°C (plus or minus 0.18°C) since the late-19th century, and the linear trend for the past 50 years of 0.13°C (plus or minus 0.03°C) per decade is nearly twice that for the past 100 years. The warming has not been globally uniform. Some areas (including parts of the southeastern U.S. and parts of the North Atlantic) have, in fact, cooled slightly over the last century. The recent warmth has been greatest over North America and Eurasia between 40 and 70°N. Lastly, seven of the eight warmest years on record have occurred since 2001 and the 10 warmest years have all occurred since 1995."
"There has been a general, but not global, tendency toward reduced diurnal temperature range [daily lows are closer to highs] ...over about 70% of the global land mass since the middle of the 20th century. However, for the period 1979-2005 the DTR shows no trend since the trend in both maximum and minimum temperatures for the same period are virtually identical; both showing a strong warming signal."
"Indirect indicators of warming such as borehole temperatures, snow cover, and glacier recession data, are in substantial agreement with the more direct indicators of recent warmth."
"Global changes in temperature extremes include decreases in the number of unusually cold days and nights and increases in the number of unusually warm days and nights. Other observed changes include lengthening of the growing season, and decreases in the number of frost days."
"For Northern Hemisphere temperature, recent decades appear to be the warmest since at least about 1000AD, and the warming since the late 19th century is unprecedented over the last 1000 years... Ice core data suggest that the 20th century has been warm in many parts of the globe, but also that the significance of the warming varies geographically, when viewed in the context of climate variations of the last millennium."
"Large and rapid climatic changes affecting the atmospheric and oceanic circulation and temperature, and the hydrological cycle, occurred during the last ice age and during the transition towards the present Holocene period. Based on the incomplete evidence available, the projected change of 3 to 7°F (1.5 - 4°C) over the next century would be unprecedented in comparison with the best available records from the last several thousand years."
"Global mean sea level has been rising at an average rate of 1.7 mm/year (plus or minus 0.5mm) over the past 100 years, which is significantly larger than the rate averaged over the last several thousand years."
"Based on paleoclimatic (proxy) reconstructions of solar irradiance there is suggestion of a trend of about +0.12 W/m2 since 1750 which is about half of the estimate given in the last IPCC report in 2001. There is though, a great deal of uncertainty in estimates of solar irradiance beyond what can be measured by satellites, and still the contribution of direct solar irradiance forcing is small compared to the greenhouse gas component."
"...the Earth's position and orientation relative to the sun (our orbit) also varies slightly, thereby bringing us closer and further away from the sun in predictable cycles. While [these] Milankovitch cycles have tremendous value as a theory to explain ice-ages and long-term changes in the climate, they are unlikely to have very much impact on the decade-century timescale. Over several centuries, it may be possible to observe the effect of these orbital parameters, however for the prediction of climate change in the 21st century, these changes will be far less important than radiative forcing from greenhouse gases."
Link to source for those of you who want to read the whole thing; emphasis my own.
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