It's based on faulty, biased number-crunching that distorts the temperature record, say Canadian researchers Stephen McIntyre and Ross McKitrick.
 
    As physics professor Richard Muller wrote in the MIT Technology Review, the two "uncovered a fundamental mathematical flaw in the computer program.
 
    Scientists Willie Soon and Sallie Baliunas of the Harvard-Smithsonian Center for Astrophysics, for example, took an exhaustive look at 240 climate studies over the past 1,000 years. They found, contrary to Mann, the 20th century was not unusually warm compared to other periods.

    Indeed, an international research group last month challenged the "hockey stick," saying the reconstruction may have underestimated past changes resulting from natural forces. For example, the earth's climate is heavily influenced by volcanic eruptions, solar flares and the position of the planet in space.

   A few years ago, R.J. Braithwaite's peer-reviewed article in Progress in Physical Geography described a "mass balance analysis" he conducted of 246 glaciers sampled all around the world between 1946 and 1995. He concluded, "There is no obvious common or global trend of increasing glacier melt in recent years."
 
   For example, a favorite melting glacier of the global warming activists sits atop Mt. Kilimanjaro in northern Tanzania, near the equator. Satellites have been measuring temperatures near its summit for more than 25 years, finding no warming at all, yet the global warmers trot out Kilimanjaro as a poster child for their cause.
 
   The scaremongers also point (to) the Antarctic continent (without addressing) the inconvenient confounding evidence -- that the continent is actually cooling dramatically. Between 1986 and 2002, the continent cooled by 0.7 degrees Celsius per decade.

   The vast East Antarctic Ice Sheet -- a 2-mile-thick wasteland of ice larger than Australia and drier than the Sahara -- increased in mass every year between 1992 and 2003 because of additional annual snowfall, an analysis of satellite radar measurements showed.

   Despite the claims of eco-activists, the science on global warming is far from settled. Consider, for one contrary example, that three different measurements of temperature change since 1979 -- surface, satellite and weather balloon -- have provided conflicting data.

   There was (a) time, not long ago, when natural gas was the most politically popular fuel around because it burns more cleanly than oil or coal.
 
   Employment in the chemical and plastic industries has fallen by 12% since natural gas prices started rising in 2000, while at least 20 fertilizer plants have closed or gone idle. This has all had a damaging knock-on effect on farmers and manufacturers.
 
   The main political bottleneck is that the professional green lobby has turned hostile to natural gas.

The Economist lists 6 indicators concerning changes seen in nature: the Earth's surface, the Artic, upper atmosphere, the world's oceans, increased + intense storms, faltering ocean currents; yet none truly, unequivocally point to man or nature's cycle.
 
The Economist continues with further possible causes; the solar hypothesis, the sun's heat output,

One option, of course is to do nothing - or at least nothing beyond eliminating the sort of economic nonsense, such as subsidising coal mining, that not only encourages global warming (because coal is the most carbon-rich fuel around), but wastes money.
 
Indeed, it is often forgotten that parts of the world would benefit from a hotter climate. In particular, the warming of the Artic is opening sea lanes that early European navigators avidly sought but were unable to penetrate. The clearing of sea ice will permit oil-drilling in places hitherto off-limits. And a gentle warming should extend the crop-growing season in places such as Canada.