Empirical evidence

Owen Jennings (Jan 16) claims the handful of scientists he refers to have evidence that human contributions to warming temperatures are minimal and there is no substantial evidence the manmade fraction of airborne CO2 causes global warming.

Goodness, if Jennings could only point to the actual cause(s), what a weight off that would be. Nobel Prize pending.

Despite constituting a fraction of the Earth’s atmosphere, it is hardly inexplicable that CO2, water vapour etc can have a profound effect on climate change. The glass or plastic enclosing a glass house takes up only a tiny fraction of the total volume enclosed yet warms the interior.

It has been estimated that without an atmosphere the Earth’s temperature would be about -18.8 degrees Celsius, so the thin layer of gases enveloping our world makes a huge difference keeping the Earth some 33C warmer than it otherwise would be.

The infrared radiation reflected back to Earth’s surface by CO2 and methane etc can be specifically measured and constitutes one piece of empirical evidence CO2 (and other greenhouse gases) are doing the warming.

There are also the real world predictive power of climate change models that claim increased CO2 will result in increased temperatures.

I would be more impressed by Jennings glib dismissal if he could offer an alternative explanation to explain this apparent association given alternatives from solar irradiance to urban heat islands have been systematically discounted.

Darren A Saunders, Waltham