IPCC report: Five Main Takeaways

The Intergovernmental Panel on Climate Change (IPCC) was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988. Its initial task, as outlined in UN General Assembly Resolution 43/53 of 6 December 1988, was to prepare a comprehensive review and recommendations with respect to the state of knowledge of the science of climate change; the social and economic impact of climate change, and potential response strategies and elements for inclusion in a possible future international convention on climate. Since 1988, the IPCC has had six assessment cycles and delivered five Assessment Reports, the most comprehensive scientific reports about climate change produced worldwide. The sixth report was published on August 9, 2021.

The Working Group I contribution to the IPCC’s Sixth Assessment report confirms that it is indisputable that human influence has warmed the climate system, raising global surface temperature. The report provides an update on the physical science basis of climate change and confirms that there is no going back from some changes that are already affecting the climate Recent changes in the climate are widespread, rapid and intensifying and impacts are affecting every region on Earth, including the oceans. Many weather and climate extremes such as heatwaves, heavy rainfall, droughts and tropical cyclones have become more frequent and severe. The report provides an atlas of regional observed and future impacts, which will allow policy makers and all other stakeholders to better inform climate policies at the regional and local levels.

The report identifies that the level of future emissions will determine the level of future temperature rise and the severity of future climate change and the associated impacts and risks. Not only have CO2 concentrations increased in the Earth’s atmosphere, but the rate of the increase has also sped up. The report shows that greenhouse gas emissions from human activities are responsible for approximately 1.1°C of warming since 1850-1900, and finds that averaged over the next 20 years, global temperature is .  to reach or exceed 1.5°C of warming.

The report’s 200-plus authors (190 scientists) distilled 14,000 individual studies to produce the release on August 9. Here are the five key takeaways from the report:

1. The last decade was hotter than any period in 125,000 years

Not only that but atmospheric CO₂ is now at a two-million-year peak. Consuming fossil fuels has combined with agriculture to push methane and nitrous oxide—also greenhouse gases—to records for at least the last 800,000 years.

All the greenhouse gases have elevated the global average temperature by about 1.1° Celsius above the late 19th century average. In fact, humans have already dumped enough greenhouse gas into the atmosphere to heat up the planet by 1.5°C—one of the goals set by the Paris Agreement—but fine-particle pollution from fossil fuels is masking it by providing a cooling effect.

The combined contribution to global warming of natural factors, such as the sun and volcanoes, is now estimated to be close to zero. Humanity has heated the climate to at least a 100,000-year high. All of the warming is caused by human influence.

2. Scientists can now link specific weather events to human-made climate change.

This hasn’t always been the case. A recently as 20 years ago, for instance, it was virtually impossible to attribute any particular storm or temperature spike to the warming world. But the climate science profession has seen entire specialties emerge and mature since the IPCC’s previous mega-report in 2013.

No field is more resonant than the ability to analyse extreme weather events in real-time to determine what role climate change is playing. The deadly heat wave that gripped the western coast of North America in June had detectable evidence of human responsibility—and that determination came quickly. World Weather Attribution, an international research group, needed just days after the heat broke to conclude that the extraordinary temperatures would be “virtually impossible” without climate change.

3. Scientists have narrowed the estimated range for how temperatures respond to greenhouse-gas emissions.

This one is a milestone in the field of climate sensitivity that’s taken four decades. Drawing from research on ancient climates, as well as advanced satellite technology that monitors clouds and emissions, new models have narrowed the projections of the atmosphere’s likely response to industrial emissions. That allowed the IPCC authors to focus their temperature projections for the rest of the century, giving humanity a clearer picture of what may lie in store if we don’t act quickly to curtail emissions.

The Earth’s response to a theoretical doubling of preindustrial CO₂ levels is now thought to be between 2.5°C to 4°C—a much smaller range than 1.5°C to 4.5°C in previous IPCC reports. These findings rule out the possibility that unrestricted emissions will have only a mild effect on global temperatures, a hope very few observers of events in recent months could cling to. But the narrower range also provides powerful evidence of the world’s best pathway to safety: swiftly ending the release of carbon dioxide and other greenhouse gases.

4. The Earth rewards good behaviour.

Almost as soon as emissions cease, heating will cease and temperatures will stabilize in a couple of decades. But some effects—such as sea-level rise—will remain irreversible for centuries. It’s a race between the avoidable and unavoidable, and humanity is behind.

Scientists broke new ground in this IPCC report by projecting what happens when our emissions get to zero. As the world reduces its use of fossil fuels, for instance, the cooling effect of aerosols will start to decline. The scientists are confident that one way to counter that decline would be to pursue “strong, rapid and sustained reductions” in methane emissions. Beyond CO₂, methane, and nitrous oxide, there are four other greenhouse gases that also provide opportunities to slow warming.

A Path to Safety: An emissions scenario that can keep global warming below 1.5°C reaches zero emissions around 2050.

5. The IPCC’s volunteer scientists build consensus with all UN governments before releasing this report.

Sometimes it’s a fight. But unanimous agreement among the nations of the world, who all must affirm that the findings are summarized accurately, is a very powerful tool. It’s what makes the IPCC the most authoritative body on global warming. The most striking takeaway in terms of the political discourse around the report is the fact that the report was approved by the 195 members of the UN; unequivocally recognising that climate change is indeed man made whilst recognizing that significant economic transformation and political consensus is cardinal to tackling climate change.

Citations:

IPCC, 2021: Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [MassonDelmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. B. R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu and B. Zhou (eds.)]. Cambridge University Press. In Press.