The Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) runs from 2021 to 2022, seven years after the previous Fifth Report, and was the first since the adoption of the Paris Climate Agreement in 2015. The next report, like the previous ones, is divided into three volumes — each volume has its own working group. The synthesis report will not be released until late 2022 or even early 2023.
The first volume of the IPCC’s Sixth Assessment Report provides an update of the physical basis of the observed global climate change. In particular, it confirms that the decisive influence on the climate today is human activity, primarily anthropogenic emissions of greenhouse gases, which have caused the average temperature in the last decade to be 1.1 °C higher than at the end of the 19th century (1850–1900). Unless there is an immediate, rapid and massive reduction in anthropogenic emissions of greenhouse gases, it will be impossible to keep the temperature rise within the 1.5 °C or even 2 °C goal (as stated in the Paris Agreement). Moreover, it is highly likely that the 1.5 °C limit will be reached and exceeded within the next 20 years.
The first volume also reports that the past five years have been the hottest on record since 1850. There is also a high probability that the past decade has been the hottest on a global scale on record. The rate of warming varies from region to region, with temperatures over land rising faster than the global average. Further warming will accelerate the melting of permafrost, glaciers and ice sheets, as well as the loss of seasonal snow cover in winter and sea ice in the Arctic in summer. Compared to the 1950s, extreme high temperatures, including heat waves, have become more frequent and intense, while low-temperature events are occurring less frequently.
Scientists note that the rate of sea-level rise has almost tripled over the past 40 years compared to 1901–1971, and further sea-level rise will lead to more frequent flooding and soil erosion. By the end of the century, extreme floods, which previously occurred once every 100 years, may start occurring every year.
Many of today’s climate changes have been described as ‘unprecedented’ compared to changes in past epochs. For example, the Summary Report uses this word 15 times (by comparison, it was used only five times in Volume 1 of the Fifth Report, and three times in the Fourth Report). It seems that scientists are tired of warning the world with the dry language of numbers and are beginning to use emotionally coloured words. And scientists are understandable, because it is so hard when you are not wanted for decades!
The second volume of the IPCC’s Sixth Assessment Report highlights the interdependence of climate, biodiversity and people, summarizing research on climate change impact assessment and adaptation measures.
It is noted that climate change has already caused serious damage to the planet. Many natural systems have reached the limits of their ability to cope with the effects of warming or are very close to doing so. For the first time, estimates are given of the consequences of climate change at different levels of warming, including global temperature increases of 1.5, 2 and 4 degrees.
Note that while the aim of the Paris Agreement is to limit warming to 2 °C above pre-industrial levels and, where possible, to 1.5 °C, current international plans and commitments call for temperatures rising to 2.7 °C. This rate of warming is a serious threat to many ecosystems. For example, shallow-water corals, suffering from repeated seawater heat waves, are unlikely to last a century, according to the report. Hundreds of plant and animal species have already disappeared from their usual habitats, some from the planet as a whole. Moreover, it is very likely that 9% of the world’s species will be at high risk of extinction with a warming of 1.5 °C. A rise to 4 °C (the most pessimistic scenario) would put 39% of species at risk! Even the most conservative estimate is a thousand times higher than the natural extinction rate.
Volume 2 also highlights that we have less time left than we thought to avoid the worst effects of climate change.
As climate change leads to homelessness, food and water scarcity, economic disruption and other threats to the lives of millions, governments must invest in protecting and restoring ecosystems, while taking social justice into account and necessarily reaching out to the poorest (societies will not be able to fully adapt unless they are socially inclusive).
The report was a wake-up call to the huge risks that climate change poses to the financial system. In some cases, the costs of adapting to these changes alone will be too high for business and governments alike. Actions taken now to limit warming to about 1.5 °C will substantially reduce projected losses and damage, but will not eliminate them altogether. Effective adaptation to climate change requires drastic measures to reduce anthropogenic emissions of greenhouse gases and to shift to sustainable development. This includes clean energy production, a circular economy, sustainable agriculture, proper urban planning and transport, universal health care, and access to water and energy for all.
The third volume of the IPCC Sixth Assessment Report reports that humanity has ample opportunity to contain global warming and thus the increase in the number and intensity of hazardous events. But it is important that these measures are taken proactively and as quickly as possible.
Current national climate targets lead to stabilisation of global warming at only around 2.7 °C by the end of the century, which would clearly make it urgent to revise them further in the long term. Keeping warming below 1.5 °C requires cutting emissions of all greenhouse gases by about half by the 2030s and reaching zero emissions of greenhouse gases in the 2050s. This will require reducing coal consumption by about 95 per cent and oil and gas consumption by 45 per cent by 2050.
As of 2019, anthropogenic greenhouse gas emissions are estimated at 53–65 billion tonnes of CO2-equivalent per year. The major part (almost 40 billion tonnes) comes from the burning of fossil fuels. Agriculture and deforestation add between 2 and 11 billion tonnes. In the previous decade, global emissions increased by 2.1% a year. Now we are also seeing an increase, but it is half as fast as it was in the 2010s.
The third volume of the report notes that radical reductions in greenhouse gas emissions will not be sufficient to meet the goals of the Paris Agreement to limit global warming. In addition, the world will need carbon dioxide capture (CDR) technologies — from planting trees that absorb carbon to costly and energy-intensive technologies that capture carbon dioxide directly from the air. However, while the potential of such technologies is limited, they cannot replace measures to reduce the carbon footprint.
To keep warming to 2 °C will also require action to limit global economic growth to between 1.3 and 2.7% by 2050. This loss is likely to be offset by the overall economic benefit of curbing the warming.
Governments will also need to implement policies aimed at changing lifestyles and behaviour, such as encouraging work from home to reduce travel, reducing car use in favour of cycling and walking, suggesting plant-based diets instead of meat consumption. This will lead to costs in some sectors but revitalise others, and prevent losses in areas such as public health. The report says that such demand-side mitigating measures could reduce global greenhouse gas emissions in some sectors by 70% by 2050.
The main message of the IPCC Sixth Assessment Report is: act now or it is too late.
Cover photo: andreygonchar / iStock
Comments