A variety of misconceptions about human-induced global warming still make the rounds of media and cocktail conversation.
The 26 world class climatologists who wrote the Copenhagen Diagnosis decided to dispel seven of the most common of them in the report, which is the first comprehensive update of leading peer-reviewed climate science in the three years since the last report of the Intergovernmental Panel on Climate Change was finalized.
They include enough detail -- though in plain language -- to communicate with common folk and policy makers alike.
Here are condensed versions of their explanations, with page-number references to the report. The full report can be read here.
QUESTION: Is the atmosphere already filled up -- saturated -- with enough CO2 so that any more won't add much warming?
ANSWER: "No, not even remotely. It isn't even saturated on the runaway greenhouse planet Venus, with its atmosphere made up of 92 percent CO2." They explain how adding more CO2 will keep warming Earth, and in the not too distant future, could warm it far beyond temperatures that civilization is prepared for. (p. 12)
QUESTION: "Has global warming recently slowed down or paused?"
ANSWER: "No. There is no indication in the data of a slowdown or pause in the human-caused warming trend." That data reflects fully the natural year-to-year up-and-down readings caused partly by natural "short-term variability" that "always has and always will be present in the climate system." (p. 15)
QUESTION: "Can solar activity or other natural processes explain global warming?
ANSWER: "No. The incoming solar radiation has been almost constant over the past 50 years, apart from the well-known 11-year solar cycle. In fact, it has slightly decreased over this period." The scientists explain that the known natural cycles and processes are accounted for in climate models. (p. 15)
QUESTION: "Isn't Antarctica cooling and Antarctic sea ice increasing?"
ANSWER: "Antarctica is not cooling. It has warmed overall for at least the past 50 years." They explain how, overall, Antarctic sea ice cover (frozen sea surface), for separate reasons involving wind changing in relation to the location of certain warming sea water currents, shows a slight upward trend, though it also shows significant melting in some areas. They also explain how the "sea ice extent around Antarctica" is very different from the sea ice in the Arctic because the Arctic is not covered by land, but by ocean, albeit mostly frozen most of the time, whereas Antarctica is a vast continent covered by massive ice sheets with the South Pole at its center. (p. 35)
QUESTION: "Isn't climate always changing, even without human interference?"
ANSWER: "Of course. But past climate changes are no cause for complacency." The scientists explain how Earth's history of climate change is precisely why scientists are so worried, since it shows both that rapid and extreme climate change has happened before and that it could easily be triggered now by human heat-trapping emissions. (p. 47)
QUESTION: "Are we just in a natural warming phase, recovering from the 'Little Ice Age'?"
ANSWER: "No. A 'recovery' of climate is not a scientific concept, since the climate does not respond like a pendulum that swings back after it was pushed in one direction. Rather, the climate responds like a pot of boiling water on the stove: it can only get warmer if you add heat." The study explains why Earth's current rapid warming is not a natural "recovery." (p. 48)
QUESTION: "Didn't CO2 rise after the warming that ended ice ages, thus showing that the melting of the ice ages -- and thus all global warming -- was not from CO2?
ANSWER: That's precisely why scientists are so worried, the report's authors explain. They know that the highly regular ice ages are caused primarily not by CO2 increases and decreases in the atmosphere but by well known wobbles in the earth's rotation -- over tens of thousands of years. What's so frightening to them is that after one of the regular warming periods begins, they can see (in air bubbles trapped in glaciers from those past times) that CO2 starts increasing, and they know that this is because of the warming and thawing of vast natural stores of carbon dioxide in the oceans -- as well as in the frozen or frigid earth of the northern tundra. Since CO2 is also a greenhouse gas -- a warming agent -- it then warms the earth even further, thawing out even more gas. The problem is that today, humankind is putting enormous amounts of the same gas in the air by burning fossil fuels and deforestation, warming the planet even further, thus thawing out even more natural stores of greenhouse gas in what they call a feedback loop. This process warms the earth even more, thawing out even more CO2. It is driving the temperature towards levels dangerous for civilization, they say. (p. 49)