Our planet is unusually cold right now; CO2 levels are  unusually low

Paul MacRae,
Times Colonist, March 9, 2008

A Victoria environmental activist was quoted in the Times Colonist in January as saying he is trying to prevent “the demise of the planet” due to climate change. No less a figure than UN Secretary-General Ban Ki-Moon said, at the Bali environmental summit in December: “One path leads to a comprehensive climate change agreement, the other to oblivion. The choice is clear.”

Is it? Are we heading for the “demise” of the planet, to “oblivion,” if carbon dioxide levels go up much beyond their current level of 380 parts per million, or if the global temperature goes up three or four or five or, for that matter, 10 degrees from its current average of 12 degrees Celsius?

If this was true then the planet and all its denizens would have died out many times in the past, because levels of carbon dioxide and the global temperature have been much higher than today for most of the past 600 million years. In fact, we’re at a 250-million-year low, teetering on the brink, not of uncontrolled global warming but of a return to ice-age conditions that the planet left only 12,000 years ago.

Take a look at Figure 1 below (you can also find it at the Geocraft website). It shows carbon dioxide levels (the black line) and temperature (blue line) over the past 600 million years, which is most of the time that life has been on the planet’s surface.

CO2 and temperature over 600 million years
Figure 1. Temperature and CO2 levels over 600 million years

Note that the average global temperature for the tens of millions of years when the dinosaurs and mammals evolved was around 22°C-10 degrees higher than today. Note that carbon dioxide levels have been up to ten times today’s levels. And yet, somehow, the plants, mammals and dinosaurs managed to survive; it took an asteroid to drive the dinosaurs into “oblivion.”

Note that, as the graph shows, carbon dioxide levels don’t have that much correlation with temperature over this time period. CO2 levels have fallen steadily for more than 150 million years, while the planetary temperature stayed at 22°C until about 30 million years ago. That’s when the planet’s temperature began its plunge into Ice Age conditions colder than anything in the past 300 million years. Our planet now is unusually cold by paleo-climatic standards, not warm. Carbon dioxide levels are unusually low, not high.

Note, too, that in 600 million years the global temperature hasn’t gone much above 22°C no matter how high the CO2 levels were. That’s because the relationship of CO2 to temperature is logarithmic: the more CO2 you put in, the less effect it has on temperature. This means there’s no need to fear “runaway” global warming due to carbon dioxide emissions.

However, most of our planet’s species (including us) would face oblivion should temperatures and/or carbon dioxide levels get too much lower. If CO2 dropped to, say, 125 ppm, there would be very little plant life and most forms of animal life would die.

Plants would thrive with more CO2

On the other hand, the plant world would thrive if carbon dioxide levels were three or four times today’s levels. That’s why hothouse growers deliberately pump carbon dioxide into their greenhouses to levels of over 1,000 ppm-the plants grow better. It’s ironic that so many “greens” oppose global warming because a world with more carbon dioxide would be a greener world, with more biodiversity, not less.

Of course, global warming does present major challenges for human beings and other species. For humans, the worst problem would probably be rising oceans, which could displace tens of millions of people. However, to say that human-generated global warming is causing the oceans to rise, as many environmental activists charge, is a simplification.

Since the last glaciation ended 12,000 years ago the oceans have risen 120 metres (400 feet), and that’s without any discernible human carbon input until the last few centuries. Ocean levels are currently rising about 4 millimetres a year (that’s a fraction of an inch).

If carbon-dioxide emissions are causing the oceans to rise, then the human contribution to this rise is a mere three per cent a year (97 per cent of carbon emissions each year are natural). So, rather than the oceans going up 40 centimetres in 100 years, which is about what the Intergovernmental Panel on Climate Change predicts, human carbon input will cause the same ocean rise in, say, 97 years, a mere three years earlier.

In other words, humanity has to deal with rising oceans whether we slash our carbon footprint or not, and a century (or 97 years) is plenty of time to prepare for the flooding.

So, are there are troubles ahead due to global warming? Of course there are if the planet keeps warming (although, in the 1970’s, the climate scientists’ “consensus” was that we were heading for another ice age).

But to say that global warming will lead to “oblivion,” to the planet “burning up,” to its “demise,” is not only untrue, it shows an astounding lack of knowledge of the planet’s climate history.

Back to home page