CLIMATE Change 2021: the Physical Science Basis —the Intergovernmental Panel on Climate Change’s (IPCC) Assessment Report 6 known as AR-6 — that was released on Monday, should send a shiver down the spine of everyone who reads it. The report has confirmed that human activities have changed our climate and are now on the verge of changing our planet forever. The report has shown that impacts will continue to increase rapidly with greater speed than scientists had predicted earlier. Only by quickly achieving net zero reductions in emissions will there be a chance of saving the world from becoming a living hell.

AR-6 is the cornerstone of climate science for the coming years. It has summarised climate change on the basis of physical science. The report has pointed out that the changes in oceans, ice-sheets, seas, and land are approaching irreversible levels and leading to abrupt changes and tipping points. The outlook is so grim that the 1.5 degrees Celsius change could happen as early as the 2030s, possibly by 2035, instead of the 2050s, as projected earlier.

The report is a sequel to IPCC’s four special reports on i) extreme events (2012), ii) global warming of 1.5°C (2018), iii) climate change and land (2019), and iv) oceans and cryosphere (2019). Providing a synthesis of 14,000 published scientific articles, and 70,000 comments, this 3,000-page report is divided into 12 chapters, based on over 100 distinct climate models by dozens of modelling groups. It includes four contributory authors from Pakistan: Irfan Tariq, Mohammad Amjad, and Mohammad Tariq, all three from the Ministry of Climate Change and Asif Khan from the University of Engineering, Peshawar. AR-6 stands out due to five key points:

The message is clear: the climate will continue to warm and weather extremes will intensify.

First, the report has resolved all major uncertainties and provided the clearest picture yet of the effect of human activities on the climate. The message is unambiguous: the climate will continue to warm and weather extremes will intensify further as long as we continue to emit CO2. AR-6 has pointed out that the temperature has been rising at a faster rate than previous IPCC assessments. The last decade was the hottest ever in centuries, not just in recorded history. A city in Sindh recorded the highest record temperature in the world.

Second, the report has increased our understanding of how quickly several worst-case scenarios will become more likely, even imminent. This is because of the tipping points, reflecting abrupt and irreversible changes. They have become more visible, resulting in non-linear reactions. Several new assessments of tipping points in the global climate system stand out in AR-6. Given the carbon stock already locked in the atmosphere, global warming will continue beyond 2100. That should not seem like a long time away, as millions of children already born during this decade should be alive well into the 22nd century. Babies born now in Pakistan, that has a huge population bulge, will experience a different world as young adults.

Third, the report has drawn attention to a global trend of compound extreme events, such as drought coupled with heatwaves, coastal flooding coupled with wind hazards, sea-level rise and storm surge, and tropical cyclones followed by heatwaves. AR-6 has confirmed, to the extent scientifically possible, what we are already experiencing in developing countries like Pakistan where climate disasters routinely alternate and coincide.

Fourth, the report has underlined the need for reduction in CO2 together with methane hitherto mostly ignored. AR-6 has underlined the importance of its reduction for improving air quality. It would counteract any future warming due to reductions in other air pollutants such as aerosols. AR-6 has highlighted a combined approach to climate and air quality that can help cleaner air while limiting climate warming. It is an urgent challenge in Pakistan where breathing clean air is becoming a rarity.

Fifth, the IPCC report has pointed out a strong link between rising temperatures and heavy precipitation, relevant particularly for Pakistan and other South Asian countries where precipitation is reported to have increased. The contributing factors include aerosols, particles, air pollutants and smoke, land-use change and water extraction. They have all impacted rainfalls from Karachi to Kolkata.

For Pakistan and for the South Asian region these global, macro-level trends result in i) wetter rainy seasons and more frequent weather events, ii) more severe wet and very dry seasons, iii) more intense heavy rains and greater flood hazards, iv) increased severity of droughts as land becomes dryer, v) increased humidity, slowing down of tropical circulation affecting warming-induced rains in monsoon regions.

In other words, the South Asian monsoon will carry substantial changes in the water cycle. AR-6 has pointed out that the Atlantic circulation, known as AMOC, that “carries heat from the tropics up to the northern hemisphere by transporting warm water masses northward at the ocean surface, and returning as a cool current southward at the bottom of the ocean”, may be approaching a tipping point. This could serve as a precursor to the weakening of the water cycle and abrupt shifts in Asian monsoon patterns that stretches from the Bay of Bengal to the Himalayas.

In all, the changes in the global systems are proportionate to carbon emissions as well as non-linear and unfairly disproportionate to global warming. AR-6 is, therefore, as much about loss & damage as about mitigation and adaptation, albeit without explicitly recognising it. L&D refers to economic and non-economic climate impacts exceeding the adaptive capacity of countries, communities and ecosystems. It is a term often associated with liability and compensation. With progress in attributive sciences where each extreme event can be attribu­ted with fair certainty to climate-induced changes, developing countries demand retribution from dev­eloped states for the climate-triggered L&D. AR-6 has provided a compendium of long-awaited scientific evidence to back up their claim with science.

AR-6 must guide the pledges, commitments and binding agreements by the world’s largest emitters led by the US, China, India, EU, UK and others. Given the scientific evidence, Pakistan’s goal at COP-26 in Glasgow in November this year, should be to align with those who favour halving global emissions by 2030 and achieving net zero by 2050, or sooner, to limit warming to 1.5C.

The writer is an expert on climate change and development.

Published in Dawn, August 14th, 2021