Climate Realities: ...It is true that, in theory, we can avoid the worst consequences of climate change with an intensive global effort over the next several decades. But given real-world economic and, in particular, political realities, that seems unlikely..., let’s look at the sobering reality.
The world is now on track to more than double current greenhouse gas concentrations in the atmosphere by the end of the century. This would push up average global temperatures by three to eight degrees Celsius and could mean the disappearance of glaciers, droughts in the mid-to-low latitudes, decreased crop productivity, increased sea levels and flooding, vanishing islands and coastal wetlands, greater storm frequency and intensity, the risk of species extinction and a significant spread of infectious disease.
The United Nations has set a goal of keeping global temperatures from rising by no more than two degrees Celsius above preindustrial levels. ... Meeting this goal would require a worldwide reduction in greenhouse gas emissions of 40 to 70 percent by midcentury, according to the Intergovernmental Panel on Climate Change. That’s an immense challenge. ...
Of course, the political climate in the United States presents its own challenges. It will require immense effort — and profound good fortune — to find political openings that can resolve the debilitating partisan divide on climate change. But if destructive politics have been at the heart of the problem, the best hope may be that creative politics and leadership can help provide a solution.
He also talks about the cost of climate change (saying it will be large), as do Peter Dorman (in response to Paul Krugman) and John Quiggin. See also Scientists Report Global Rise in Greenhouse Gas Emissions.