‘Climate change is for real, 100% certainty that it is caused by human activity’

The Intergovernmental Panel on Climate Change (IPCC) on Monday came out with its sixth assessment report on the science of climate change based on the review of over 14,000 published papers by 234 scientists across the world. One of the scientists, Govindasamy Bala of Bengaluru’s Indian Institute of Science, spoke to Chetan Chauhan about the findings of the report. Edited excerpts:

What is the main takeaway of the report?

It is IPCC’s guidance on the global mean rise in temperature by 1.5-degrees Celsius (°C) by the turn of this century for policymakers and input on negotiations. The key message is the statement of fact that climate change is for real and there is 100% certainty that it is caused by human activity. For me, it is a major breakthrough as compared to past assessments where IPCC used to say the same thing with 99% surety.

The second important factor is the rapid speed of climate change. In 100 years, the temperature has risen by 1°C. It may appear normal to people. But compare it with temperature rise in 4.5 billion years. You will see it is a rapid increase in temperature. And it is because of 410 billion particles per million of carbon dioxide in space.

Has the weather become more extreme?

Yes. See this year, Canada, normally considered a cold country, had (almost) 50°C temperature. Austria also had a similar temperature this summer. If we see data, there are several extreme day events, especially heatwaves and rains, caused by human influence. This is because of the warmer background which magnifies rainfall manifold. And the report tells us the manifestation of climate change would be extremes.

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What would be these extremes like?

For instance, the sea level rise would be 80 centimetres by the turn of the century. But if ice sheets in Greenland and Antarctica collapse, the rise can be up to 8 metres. Heatwaves across the world would rapidly increase and the intensity of monsoons would go up and these factors may impact agriculture output.

Paris climate deal set a target of limiting temperature rise to 2 degrees Celsius. Will that happen?

In the present business as usual scenario, we may not be able to limit temperature rise to 2°C. Surely, we are losing time to limit temperature to 1.5°C, an ambition outlined in the Paris agreement. We may be looking at 2.7°C. But the world can achieve 1.5°C also if we start reducing carbon emissions now. For this, we need to work towards net zero. The IPCC report has delved into different net-zero scenarios, which can provide guidance to climate negotiators. We have found that net-zero by 2070 would lead to a 2°C temperature rise. 2050 would lead to a 1.5°C temperature rise.

Many countries like India are opposed to net zero as of now...

Carbon emission is increasing. It has reached 4.4 billion tonnes per year. The carbon budget at the present rate of emissions will be exhausted in 10 years. There is no bell curve in carbon emissions; it is a long curve. This is what science says.