The people who favor actions like Waxman-Markey, the imposition of fleet average fuel efficiency standards, and the treatment of CO2 as a regulated pollutant generally claim that the costs involved are justified by the need to head off anthropogenic global warming.
The fundemental catechism taught by "warmists" is that some part of the solar radiation absorbed by soil and other ground level material bounces back into the atmosphere as infrared (heat) radiation; that greenhouse gases in general, and CO2 in particular, capture this heat in the atmosphere; that cumulative human caused emissions of these greenhouse gases are reaching a threshold beyond which they will produce a runaway greenhouse effect in earth's atmosphere; and that the resulting global warming will produce catastrophic flooding and other effects leading to a billion deaths by 2100.
Meanwhile the Sun seems now to be finally coming out of what has been the longest period of minimum sunspot activity since the the cycle ushering in the Dalton minimum - a 40 year period during which crops froze across America and people across Europe starved.
Compounding this, world food stocks are already near historic lows -thus the recent diversion of a significant fraction of the American corn crop into biofuels led to food riots in Mexico and increases in food pricing, particularly for meat, around the world.
This looks like two competing scenarios: one based on destruction by fire, the other by ice, but there are enormous consequential and behavioural differences between the two camps. On the behavioral side, only the warming side is shouting; there is no identifiable group, and thus no howling mob, warning of cooling - only individual scientists collecting data and muttering among themselves.
On the consequential side there is no doubt that worldwide starvation would be a bad thing and equally no doubt that life likes warmth and water: that a warm planet supports more life, and a greater diversity of life, than one made up largely of glaciers or desert.
In other words:
Warming, in other words, has lots of winners, stability makes fools of warmists but is naturally accomodated, and cooling is disasterous -but which is really more likely?
The bottom line on the evidence for anthropogenic global warming is absolutely astonishing: there isn't any.
On the statistical side the historical record from ice cores and other sources consistently shows atmospheric CO2 concentrations changing well after, never before, significant climate changes - in both directions. The short term record, meanwhile, suggests that tropospheric CO2 concentrations have roughly doubled over the last two hundred years - with no measureable impact on climate.
On the theoretical side, the claimed effects of atmospheric CO2 have never been empirically demonstrated - it's obvious that a fixed volume of air will hold more heat if some of the air is replaced by CO2, but that's because CO2 is denser than air, and not because it acts as an atmospheric one way valve for infrared radiation. On the contrary, physicist R. W. Wood showed (in 1909) that adding CO2 to the air in a ground level solar greenhouse led to better plant growth but not to higher temperatures; and, of course, because CO2 is heavier than air only a very small fraction (significantly less than 1%) of CO2 emitted at or near ground level ever makes it into the upper atmosphere - the run-away greenhouse phrase itself, by the way, comes from Ingersoll's 1969 paper on the effects of water vapor on Venus.
It seems absurd, but the whole CO2 as climate driver claim has neither a statistical basis nor theoretical support - what it has, is believers. Thus the press release and summary accompanying a recent paper showing "that natural forces are the dominant influence on climate" (McLean, J. D., C. R. de Freitas, and R. M. Carter (2009), Influence of the Southern Oscillation on tropospheric temperature, Journal of Geophysical Research, 114, D14104, doi:10.1029/2008JD011637) included this quotation from one of the lead authors:
When climate models failed to retrospectively produce the temperatures since 1950 the modellers added some estimated influences of carbon dioxide to make up the shortfall
In contrast the people who argue that things like solar radiance and sun spot activity are correlated with climate and therefore that the current minimum predicts global cooling, have statistics on their side in that the correlation is easily demonstrated from past data and seems, so far, to be predictive in terms of recent weather.
They do not, however, offer a compelling theory of causation - although experiments conducted at CERN and now being extended tend to support Svensmark's Galactic Cosmic Ray (GCR) cloud cover modulation theory.
So when we ask whether the earth is currently undergoing either unusual warming or unusual cooling, the right answer is that nobody really knows today; that nobody will know until we have a sufficiently good grasp of the measures and causes of climate change to make precise predictions that turn out to be accurate; and that, on balance, cooling may be more likely and is certainly far more destructive than warming.
Given that, the indicated policy response for republicans seems clear: start by publically doing what environmentalists won't: recognize that global warming is environmentally desireable, global temperature stability marginally less so, and global cooling distinctly undesireable - and go from there to simualtaneously supporting more work on the science while quietly building a hedge or two against the effects of cooling.