Is Global Warming Man Made?

"Climate change policy: IPCC consensus is not enough."
Terradas J, Peñuelas J. Ambio. 2008 Jun;37(4):321-2.

In the four years since my original review (Keller[25]; hereafter referred to as CFK03), research has clarified and strengthened our understanding of how humans are warming the planet. ...

The big news since CFK03 is the first of these, the collapse of the climate critics' last real bastion, namely that satellites and radiosondes show no significant warming in the past quarter century. Figuratively speaking, this was the center pole that held up the critics' entire "tent." Their argument was that, if there had been little warming in the past 25 years or so, then what warming was observed would have been within the range of natural variations with solar forcing as the major player. Further, the models would have been shown to be unreliable since they were predicting warming that was not happening.

"Improving communication of uncertainty in the reports of the intergovernmental panel on climate change."
 Budescu DV, Broomell S, Por HH. Psychol Sci. 2009 Mar;20(3):299-308.

You have undoubtedly read the story about a breakup of a massive glacier in the Antarctic, supposedly showing the ever-increasing effects of global warming. Yet we don't hear that the area was ice-free, possibly just some 400 years ago, without the help of global warming. We don't hear that the Wilkins glacier makes up less than 0.01% of Antarctica. And we don't hear the inconvenient fact that the Antarctic is experiencing record sea ice coverage since satellite measurements began.

While we all heard Al Gore talking about the dramatic hurricane years of 2004 and 2005, we've heard almost nothing about the complete absence of hurricane damage in 2006 and 2007. ...

We are constantly presented with the stories underlining how temperatures are soaring, but over the past year, when temperatures worldwide have plummeted, we've seen the single fastest temperature change every[sic] recorded, either up or down. Yet, this rarely gets mentioned, although stories abound. In January, Hong Kong was gripped with the second longest cold spell since 1885. ... Snow fell on Baghdad for the first time in living memory.

... almost all politicians in most nations are scuffling to promise ever stricter CO2 cuts. This is evident also in the United States, where, as of this writing, all three major presidential candidates have set forward elaborate promises to deliver significant carbon reductions till[sic] by 2050. However, there is very little information on both the efficiency of such policies (how much less warming will we see?) and their costs (how many billions of dollars will it cost?). And for good reason. As you see on page 132 of this book, Al Gore's proposal for a $140 carbon tax would hike gas prices by $1.25 per gallon, cut the U.S. emissions by half in 2015, yet have an almost immeasurable impact on temperatures--decreasing the average temperature in 2100 by 0.2 [degrees] F. And the cost would be a dramatic $160 billion annually for the rest of the century.

Hard to know where to start here.

Climate model simulations cannot explain the anomalous late 20th century warmth without taking into account the contributions of human activities, the authors say. They make three major points regarding Soon and Baliunas's recent assertions challenging these findings.

First, in using proxy records to draw inferences about past climate, it is essential to assess their actual sensitivity to temperature variability. In particular, the authors say, Soon and Baliunas misuse proxy data reflective of changes in moisture or drought, rather than temperature, in their analysis.

Second, it is essential to distinguish between regional temperature anomalies and hemispheric mean temperature, which must represent an average of estimates over a sufficiently large number of distinct regions. For example, Mann and his co- authors say, the concepts of a "Little Ice Age" and "Medieval Warm Period" arose from the Eurocentric origins of historic climatology. The specific periods of coldness and warmth differed from region to region and as compared with data for the northern hemisphere as a whole.

Third, according to Mann and his colleagues, it is essential to define carefully the modern base period with which past climate is to be compared and to identify and quantify uncertainties. For example, they say, the most recent report of the Intergovernmental Panel on Climate Change (IPCC) carefully compares data for recent decades with reconstructions of past temperatures, taking into account the uncertainties in those reconstructions. IPCC concluded that late 20th century warmth in the northern hemisphere likely exceeded that of any time in the past millennium. The method used by Soon and Baliunas, they say, considers mean conditions for the entire 20th century as the base period and determines past temperatures from proxy evidence not capable of resolving trends on a decadal basis. It is therefore, they say, of limited value in determining whether recent warming in anomalous in a long term and large scale context.

American Geophysical News, 2003