by Larry Bell
Dismissing the recent 17 years or so of flat global temperatures, the IPCC will assert that: “It is extremely likely that human influence on climate caused more than half of the observed increase in global average surface temperature from 1951 to 2010.”
The draft report also says “There is high confidence that this has warmed the ocean, melted snow and ice, raised global mean sea level and changed some climate extremes in the second half of the 20th century.” And whereas the IPCC’s previous report modestly claimed a 90% chance that human activities were the cause, they’re now ratcheting up their confidence level to 95%.
Obviously then, they must have some very strong evidence to back this amplified bluster. Right? Well, then again, maybe not so much after all.
What Evidence Exists of Unnatural Recent Global Warming?
Cyclical, abrupt and dramatic global and regional temperature fluctuations have occurred over millions of years. Many natural factors are known to contribute to these changes, although even the most sophisticated climate models and theories they are based on cannot predict the timing, scale (either up or down), or future impacts- much less the marginal contributions of various human influences.
While global warming has been trumpeted as an epic climate change crisis with human-produced CO2, a trace atmospheric “greenhouse gas” branded as a primary culprit and endangering “pollutant,” remember that throughout earlier periods of Earth’s history CO2 levels have been between four and eighteen times higher than now, with temperature changes preceding, not following atmospheric CO2 changes.
Has there been “recent” warming? Yes, the global climate has definitely warmed since the Little Ice Age (about 1400-1700 AD), and it will likely continue to warm for another 200-300 years, in fits and starts, towards a max temp roughly matching that of the Medieval Warm Period. That time followed a colder period before the founding of Rome between about 750 BC to 200 BC. By 150 BC the climate had warmed enough for the first grapes and olives to be cultivated in northern Italy. As recently as 1,000 years ago, Icelandic Vikings were raising cattle, sheep and goats in grasslands on Greenland’s southwestern coast.
Then, around 1200, temperatures began to drop, and Norse settlements were abandoned by about 1350. Atlantic pack ice began to grow around 1250, and shortened growing seasons and unreliable weather patterns, including torrential rains in Northern Europe, led to the “Great Famine” of 1315-1317.
Temperatures dropped dramatically again in the middle of the 16th century, and although there were notable year year-to-year fluctuations, the coldest regime since the last Ice Age (that so-called “Little Ice Age”) dominated the next hundred and fifty years or more. Food shortages killed millions in Europe between 1690 and 1700, followed by more famines in 1725 and 1816. The end of this time witnessed brutal winter temperatures suffered by Washington’s troops at Valley Forge in 1777, and Napoleon’s bitterly cold retreat from Russia in 1812.
Although temperatures have been generally mild over the past 500 years, we should remember that significant fluctuations are normal. The past century alone witnessed two distinct periods of warming. The first occurred between 1900 and 1945, and the second, following a slight cool-down began quite abruptly in 1975. That second period rose at very modest rate, if at all, until 1998, and then stopped and began falling again after reaching a high of 1.16ºF above the average global mean temperature. There hasn’t been any warming for at least a decade and a half, and possibly, considerably longer.
It’s also worth remembering that about half of all estimated warming since 1900 occurred prior to the mid-1940s despite continuously rising CO2 levels. Also consider that, even today, about 97% of all current atmospheric CO2 derives from natural sources.
What Evidence Exists of Human CO2 Influences on Climate?
All IPCC climate models incorporate theory which predicts that “anthropogenic” (human-caused) global warming will be evident in an “amplification” of a surface warming trend that is revealed as an atmospheric “hot spot” in the tropical troposphere. Instead, both satellite data and independent balloon data show a near-zero trend from 1979 to 1997, followed by a well-known 1998 temp “spike” which is universally attributed to a Super-El- Niño. This absence of an observed hot spot suggests that the land-surface temperature warming trend (1979-1997) is greatly overestimated, and should be close to zero in the Tropics.
So where does the evidence needed to support the IPCC’s 95 percent certainty claim come from? The true answer is that there simply isn’t any. None at all. There never was…only totally unproven theoretical climate models.