Best Evidence

The impact of mankind on our planet is now so great that our species is increasingly being recognised as a geological force of nature. We even have our own geological era, the recently coined Anthropocene, or Age of Man.

Given this, it is timely to look again at the evidence for anthropogenic, or man-made, climate change. There are only two charts that we need to look at to fully understand the critical need to act on climate change (the “why” question) and here they are:

These charts, using data from the Vostok ice core in the Antarctic, track temperature and CO2 concentrations back more than 400,000 years.

The data are rich and tell many stories. However, there are a number of key features worth highlighting:

  1. CO2 and temperature march in lock step. When one goes up, the other goes up. When one goes down the other goes down. This is entirely consistent with the physics of the CO2 molecule (and other greenhouse gases). They are all perfectly sized to absorb infra-red radiation, which is given off by the planet as the sun’s rays warm its surface, and to retain that energy in the atmosphere. And thank goodness for that, otherwise the earth would be a lifeless, icy lump of rock whizzing around the sun.
  2. The climate is naturally variable. The deniers are right on this point, at least. Modern man emerged, we believe from a common ancestor in Africa, about 150,000 years ago. The industrial revolution started only some 250 years ago. So the variations shown in the data are entirely natural. However, these natural variations take place very slowly in human terms, changing over many thousands of years.
  3. There is a natural “trading range”. Over the 400,000 year history shown in the data, CO2 moves within a clearly defined range from 180 parts per million (ppm) to 280 ppm. Likewise, temperature moves within a range of plus or minus 10°C.
  4. The last 10,000 years have been unusually temperate and stable. In this period, mankind has blossomed to become the dominant species on the planet. We discovered agriculture, began the transition from hunter gatherers to settled communities and, above all, we exponentially grew in number. It took until around the year 1800 to reach 1 billion humans, but there are now nearly 7 billion of us and there are forecast to be more than 9 billion by 2050.

“Well that’s all very interesting but so what?” an observer might say.

Well, what the charts don’t show (because it’s so recent) is that in the last 150 years or so, we have smashed out of the historic CO2 range. We are now at over 380 ppm and climbing fast. We have added as much new CO2 as the entire previous trading range. Never before has CO2 increased so much, so quickly. And it has happened almost overnight, in the blink of an eye. We are in uncharted territory in human history and, if we do nothing about it, CO2 will soon be at 400, 500, even 1000 ppm.

Do we just take the risk that, this time, temperature won’t follow CO2? (Although unfortunately, all the observational data tells us that it is already inching up.) Do we punt humanity’s future because denial is easier than action? Or do we adopt a prudent approach, a risk management approach, and take action now to reduce new emissions and to sequester the carbon that we have already pumped into the atmosphere?

This is a really easy choice. We don’t need to hear doomsday scenarios of the impacts of increased temperatures on Earth’s capacity to support humanity (although many exist and they make for uncomfortable reading). We just need to manage risk. Think of it as insurance.

And that’s why the carbon debate can end in only one outcome – a clear call to action.


Source:  Freddy Sharpe CEO, Climate Friendly.  October 2011.


About Alan

Settling into my 7th decade and still determined not to grow up too soon.
This entry was posted in Life, don't talk to me about life!. Bookmark the permalink.

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