There is no serious debate any more about one thing: More of these gases will cause more warming. Lindzen, who contends that any human climate influence is negligible and has long criticized those calling global warming a catastrophe, agreed on this basic fact in his article.
At the same time, few scientists agree with the idea that the recent spate of potent hurricanes, European heat waves, African drought and other weather extremes are, in essence, our fault. There is more than enough natural variability in nature to mask a direct connection, they say.
Even recent sightings of drowned polar bears cannot be firmly ascribed to human influence on climate given the big cyclical fluctuations of sea ice around the Arctic.
The unresolved questions concern the pace and extent of future warming and the impact on wildlife, agriculture, disease, local weather and the height of the world's oceans - in other words, all of the things that matter to people.
The latest estimates, including a study published in the journal Nature, foresee a probable warming of somewhere around 3 degrees Celsius (5 Fahrenheit) should the concentration of carbon dioxide reach twice the 280- parts-per-million figure that had been the norm on earth for at least 400,000 years. This is far lower than some of the apocalyptic projections in recent years, but also far higher than mild warming rates focused on by skeptics and industry lobbyists.
As a result, by 2100 or so, sea levels could be several feet higher than they are now, and the new norm on the planet for centuries thereafter could be retreating shorelines as Antarctic and Greenland ice sheets relentlessly erode.
Projections of how patterns of drought, deluges, heat and cold might change are among the most difficult, and will remain laden with huge uncertainties for a long time to come, said M. Granger Morgan, a physicist and policy expert at Carnegie Mellon University in Pittsburgh.
For example, while computer simulations of the climate consistently show that the centers of big continents are likely to grow drier, and winters and nights generally warmer, they cannot reliably predict conditions in Chicago or Shanghai.
By the clock of geology, this climate shift is unfolding at a dizzying, perhaps unprecedented pace, but by time scales relevant to people, it is happening in slow motion. If damage does not happen for 100 years or so, it is hard to persuade governments or voters to take action.