Are man-made greenhouse gas emissions causing the warming?

The answer is both yes and “don’t know”.

Yes, because the greenhouse effect from CO2 has been known for years, tested a thousand times in the lab, and CO2 levels are rising. It’s basic physics.

But “we don’t really know”, because other factors, sunspots, clouds, reflecting snow, as well as positive and negative feedback loops also affect things. Sure we’ve got climate models, and some do OK.  But we’ve only got one climate, so it’s difficult to test the models properly.

Many sceptics cite past associations of warming with sunspot cycles, and imperfect relations between temperature and CO2 in various data sets. But none of that refutes the alarmist case. They know the relation is complex. It is indisputable that CO2 is a greenhouse gas, levels have risen sharply over the last 150 years and it remains the most likely explanation for the temperature rise seen over the latter half of that period.

Whether the warming will continue is hard to predict. But continuing to burn fossil fuels will release more CO2, and the greenhouse gas effect isn’t going away. Hopefully there will be some negative feedback; maybe rising CO2 will increase plant growth and natural carbon capture. On the other hand perhaps the tundra will thaw and cause runaway CO2 release and more warming. Volcanoes and sunspots will surely mess up detailed predictions.  But the alarmists best estimates that in the long run the warming will continue if we keep burning fossil fuel are surely correct.

Two: nil to the alarmists! You’ll be wondering – am I really a sceptic?

Tomorrow a look at the damage the warming might do.

Jim Thornton