Parsa Venkateshwar Rao Jr

Senior Journalist

The Inter-governmental Panel on Climate Change (IPCC)’s Sixth Assessment Report (AR6), released this year, has some useful, scientific caveats. It would be good to keep them in mind when we heatedly debate the climate change crisis moving towards a climate change catastrophe. It is rightly titled ‘Climate Change 2021: The Physical Science Basis’.

The first caveat is about what is meant by the pre-industrial levels. The report says, “…warming is expressed relative to the period 1850-1900…” There is also a shorter 30-year span used as a framework to measure the increase in temperatures. Going by the 1850-1900 timeframe, the report says that the human-induced warming reached approximately 1°C — and there is a caveat within the caveat that the increase ranged from 0.8°C to 1.2°C — above the pre-industrial levels in 2017, and the warming from the pre-industrial levels to the decade of 2006-15 is “assessed to be 0.87°C (likely between 0.75°C and 0.99°C).” The decimal placing is important because accuracy is the heart of the matter. It gives the perspective to understanding the challenge and find the right responses.

Since 2000, the report says, the “estimated level of warming” is 20 per cent plus/minus, and this is necessary to account “for uncertainty due to contributions from solar and volcanic activity over the historical period...”

This is, indeed, the cautionary note, acknowledging the fact that there are factors other than human-induced activity which could cause an increase in temperatures over a period. This is also an indirect acceptance that we do not, as yet, have the exact numbers to measure solar and volcanic activity.

The other caveat is about the unevenness of global warming. Global warming is defined in this report as “an increase in combined air and sea surface temperatures averaged over the globe and over a 30-year period.”

But it is conceded that the temperature rise over land surface was greater than that over the sea surface. “Most land regions are experiencing greater warming than the global average, while most ocean regions are warming at a slower rate.”

Then, we come across an intriguing, and politically contentious caveat: “Past emissions are unlikely to raise global-mean temperature to 1.5°C above pre-industrial levels (medium confidence), but past emissions do commit to other changes, such as further sea level rise (high confidence).”

If the human-induced emissions are reduced to zero immediately, then the rise in temperature would most likely be less than 0.5°C over the next two or three decades, and it would likely be less than 0.5°C over the century.

And the report draws the ambiguous conclusion: “1.5°C pathways are defined as those that, given current knowledge of climate response, provide a one-in-two to two-in-three chance of warming, either remaining below 1.5°C or returning to 1.5°C by 2100 following an overshoot.” The ‘overshoot’, of course, has serious implications, but it can return to the optimum of 1.5°C.

It is also argued that there are two ways of limiting the impact of cumulative emissions. One is to take preventive action, and the other is remedial action. The report says, “There is no single answer to the question of whether it’s feasible to limit warming to 1.5°C and adapt to the consequences.”

The report projects different climate scenarios for a 1.5°C rise and a 2°C rise. For example, about a ‘sea-ice-free Arctic Ocean’, the projection is: “Model simulations suggest that at least one sea-ice-free Arctic summer is expected every 10 years for global warming of 2°C, with the frequency decreasing to one sea-ice-free Arctic summer every 100 years under 1.5°C (medium confidence).”

The new factor that has emerged in the discussions on climate change is the deleterious role of agriculture in climate and environmental degradation. The popular argument has been that it is the industrial revolution that began at the end of the 18th century in Europe that is the evil behind the climate crisis. That is why the talk has been about reducing carbon emissions and all that to the pre-industrial levels.

But it has now become evident that large agriculture, including dairy farming, of the last hundred years and more, is contributing hugely greenhouse gas emissions. There is now the felt need to regulate and constrict agriculture to mend the climate situation.

Of course, some activists would argue that it is the industrialisation of agriculture that is the problem, and not agriculture as such.

Climate scientists have not yet spoken on this. But in the new scenario, the pastoral and the romantic pieties associated with it go out of the window. The decisions to be taken around mitigating measures to control carbon emissions become all the more politically contentious.

The argument is in favour of limiting the rise in temperature to 1.5°C, and the promise made that 1.5°C is compatible with the UN Sustainable Development Goals (SDGs) and eradication of poverty. The report says, “Limiting global warming to 1.5°C rather than 2°C above pre-industrial levels would make it markedly easier to achieve many aspects of sustainable development, with greater potential to eradicate poverty and reduce inequalities (medium evidence, high agreement).”

Much of the rest of the IPCC report is prescriptive, looking at drastic reductions in coal, gas and oil for energy, reducing the carbon intensity of electricity generation, and increasing the share of renewable sources to nearly 70 per cent.

The more difficult is the target of reducing agriculture as we know it, decreasing pastureland and crop land, while increasing the forest cover. Perhaps, there is no alternative but to change the pattern of modern production, in both industry and agriculture.

But the climate agenda stands on quicksand as it were because the caveat is that climate agenda must be compatible with SDGs. This is the impossible task of squaring the circle.