Are headlines trumpeting the fact that carbon dioxide levels in the earth’s atmosphere have now passed the crucial 400 parts per million for the first time in something like three million years unduly alarmist? Or are they a timely warning?
The current CO2 concentration of 400 ppm is some 40 percent higher than anything that has been attained in the last 800,000 years. The glacial-interglacial cycles began some two and a half million years ago. Scientists estimate that a CO2 concentration of 400 ppm has not been attained for at least 3 million years. This rapid a change in CO2 concentrations has probably not occurred for tens of millions of years.
The point here is that we are undertaking a colossal planet-wide experiment of injecting CO2 into the atmosphere that goes extraordinarily further and faster than anything within the range of natural CO2 fluctuations for tens of millions of years. The result is a great deal of uncertainty about the possible outcomes of this experiment. The higher the concentrations of CO2, the further outside the range of normal fluctuations is the planet, and the more unsure are we about the consequences.
Carbon dioxide is a greenhouse gas. It is by now (and for some considerable time has been) beyond any reasonable doubt that increased levels of atmospheric CO2 lead to increased average temperatures. What is still uncertain and the subject of legitimate debate is the magnitude of this effect: how much CO2 leads to how much warming?
What is even more scary, and maybe even catastrophic, is the speed at which we blew right past 400 ppm of CO2, with no visible end in sight — and what that might portend for ultimate global warming.
If we were to continue CO2 emissions up to an atmospheric concentration of 600 ppm of CO2, the IPCC formula translates into an ultimate average temperature change of 3.3 C (5.9 F) with a likely range between 1.1 C (2 F) and 5 C (8.9 F).
If we were to continue CO2 emissions to an atmospheric concentration of 800 ppm of CO2, the IPCC formula translates into an ultimate average temperature change of 4.5 C (8.2 F) with a likely range between 3 C (5.4 F) and 6.8 C (12.3 F).
The world has not seen this level of CO2 concentrations for some 50 million years, when crocodiles and palm trees thrived in the Arctic Circle, Greenland and Antarctica were ice-free, and sea levels were many thousands of feet higher than today.
Here are some questions we should be asking ourselves:
- What will be the effects of higher temperatures on precipitation patterns?
- Will monsoon rains be greatly altered?
- What will happen to Indian or Bangladeshi agriculture?
- Will dry places in Africa become even drier?
- Will tropical storms intensify?
- When will the ice sheets covering Greenland and West Antarctica begin to melt seriously, thereby sharply raising worldwide sea levels?
- Will basic essential patterns of ocean circulation currents be changed?
- Will the Amazon rain forest dry out or die back?
- Will there be large-scale releases of currently contained CO2 and methane (an even more potent greenhouse gas) under melting permafrost, thereby accelerating the process of global warming itself?
- What about the truly stupendous amounts of methane trapped inside the offshore continental shelves by low temperatures — might they start to become unstuck by higher ocean temperatures, thereby triggering a vicious global warming circle?
- What will be the effects of large-scale rapid melting of ice in the Arctic Ocean?
- What about the unknown unknowns we have not even thought of?
Paul Solman just held an excellent interview with Martin L. Weitzman, Professor of Economics at Harvard University that goes into greater detail and brings up some excellent points and analysis. Click here to read the full article.