On 9 August 2021 Monday, the United Nations Intergovernmental Panel on Climate Change (IPCC) released a landmark report demonstrating that human activities have caused ‘unprecedented’ and ‘irreversible’ change to Earth’s climate.
This report is named “Climate Change 2021: the Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change”. It is compiled by 234 scientists from 66 countries, distilling more than 14,000 scientific studies. It is an up-to-date summary not only for policymakers but also for the public.
According to the Working Group I report, climate change and extreme weather events driven by global warming resulted from huge amount of annual greenhouse gas emissions are taking hold in every region of Earth. In recent years particularly, climate changes are “widespread, rapid and intensifying” and are affecting every ecosystem on Earth, including the oceans.
This report shows that on average global surface temperature is approximately 1.1°C higher in the decade between 2011-2020 than between 1850-1900. Indeed, meteorological reports have already documented that the past five years have been the hottest on record since 1850.
Following the 2015 Paris Climate Agreement of limiting global warming to 2.0°C above pre-industrial levels (1850-1900) by the end of this century, an IPCC special report released in 2018 has advocated a goal of keeping the increase of global average temperature to 1.5°C above pre-industrial levels. However, the latest IPCC Working Group I report finds that the increase of global average temperatures will reach or exceed 1.5°C by 2040 under all emissions scenarios.
In the IPCC’s last climate assessment released in 2013, it was estimated that the probable range of increases in the global average temperature was 1.5–4.5 °C above the pre-industrial levels by the end of this century. The latest IPCC Working Group I report has further narrowed the probable range of increases in global temperature to 2.5–4 °C, using modern and ancient climate records.
The latest IPCC Working Group I report projects that the negative impacts of climate warming are far more severe when the temperature increase is greater than 1.5°C. “For 1.5°C of global warming, there will be increasing heat waves, frequent droughts and flooding, longer warm seasons and shorter cold seasons. At 2°C of global warming, however, heat extremes would more often reach critical tolerance thresholds for agriculture and human health”.
In the IPCC’s last assessment released in 2013, it was documented that humans were the “dominant cause” of global warming since the 1950s. In the latest IPCC Working Group I report, it is further confirmed, in strong and confident tones, that “it is indisputable that human influence has warmed the climate system, raising global surface temperature.”
For some professionals, as stated by Prof. Katharine Hayhoe, “the headlines of the IPCC Working Group 1 report are no surprise. We have known them for years.” However, this report is the first major review of the scientific findings in climate change since 2013. It is the most up-to-date and comprehensive assessment of how climate warming will change the world in the coming decades. “Their power lies in the starkness with which they are presented.”
According to the UN Secretary-General’s statement, the IPCC Working Group 1 Report is “a code red for humanity”. This report provides updated knowledge of the physical basis of climate change – the core underlying science – and confirms that there is no chance to go back from some changes that are already affecting the Earth’s climate system. “The alarm bells are deafening, and the evidence is irrefutable.”
More importantly, the IPCC Working Group 1 Report has been approved by the delegations of 195 governments. This means that it will allow policy makers in almost all countries and all other stakeholders to better inform climate policies at the regional, national, and local levels.
The Working Group I report is the first instalment of the IPCC’s Sixth Climate Assessment Report. The IPCC has three working groups: Working Group I deals with the physical science basis of climate change; Working Group II deals with impacts, adaptation and vulnerability; and Working Group III deals with the mitigation of climate change. Two further instalments undertaken by the other two groups will be released in the next year.
Sound policy and effective actions are based on solid scientific findings. As the IPCC’s latest report underscores, effectively mitigating climate change can only be achieved through rapid implementation of more ambitious, significantly scaled-up reduction of greenhouse gas emissions, which need everyone’s contribution and participation. Otherwise, it would be a great challenge for sustainable development worldwide and for future human generations’ health and well-being.