Limpopo Province in South Africa, where climate change is leading to an increasingly arid environment (Julia K Green/Columbia Engineering)

Professor Richard Tuckett writes for the Birmingham Perspective:

Since 2015 there have been three UN-sponsored conferences on climate change: Paris in December 2015; Inchon in South Korea in October 2018; and Katowice in Poland in December 2018.

Paris set the framework. All countries must act collectively if the Earth’s temperature by the end of this century can be limited to 2 degrees Centigrades above that before the Industrial Revolution 150 years ago. Inchon said 2 degrees was too much, and all countries should aim for 1.5 degrees. Katowice set the ground rules about how these temperature increases could be monitored and measures to limit them implemented.

No reputable scientist now disputes the phenomenon of climate change. This was not the case 10 years ago, but Inchon raised eyebrows with headline summaries. Global temperatures are currently increasing at 0.2 degrees per decade. We are already 1 degree above pre-Industrial Revolution levels, so could reach 1.5 degrees within 25 years.

Global emissions of carbon dioxide need to fall by 45% from 2010 levels by 2030 and must reach zero by 2050 if we are to hit 1.5 degrees. If not, the runaway greenhouse effect will kick in with disastrous consequences — temperature rise by 2100 could exceed 3 degrees.

Only one number has changed significantly over the last six decades: the total radiative forcing of all secondary greenhouse gases, caused by an increasing atmospheric concentration of carbon dioxide. In 1960, the concentration was 1.17 Watts per square metre. In 2013 it was 2.83, and now it is probably slightly higher, with a rise from 310 to just above 400 parts per million by volume.

The other important figure has not changed. Two gases, carbon dioxide and methane, make up 80% to 85% of the contribution to the greenhouse effect, with the former’s impact about 3.5 times that of the latter. Yes, there are more gases contributing to the greenhouse effect than was appreciated 60 years ago. Yes, some of the finer details of infrared radiative efficiencies and global lifetimes of greenhouse gases are much improved. But these are small effects.

An individual can wear more clothes and turn down room temperatures, fly and drive less, and become vegetarian, but this will have negligible effect if it is one person out of 7.4 billion people. Governments have to step in and impose policies that, by force of law, affect every person in that country. World organisations will need to set global policies, with the UN the only serious possibility to lead this through measures such as carbon taxes and desired levels of world population.

If climate change is not controlled, global migration of people from the low-lying countries of the Southern Hemisphere to high-lying countries in the Northern Hemisphere will happen on a scale that will make the current issues in Europe seem miniscule.

After these three conferences, we cannot say we were not warned.