Major intergovernmental report on the science of climate change and the consequences for policymakers released by IPCC

09 Aug 2021

Planning and Environment, Cornerstone Climate

On 9 August 2021, the Intergovernmental Panel on Climate Change (IPCC) released the first instalment of its Sixth Assessment Report (due to be completed in 2022), concerning the physical science basis of climate change. The IPCC is the UN body for assessing the science related to climate change. Estelle Dehon considers the headline conclusions of the Report, and its potential ramifications.

Headline Conclusions

Some of the most significant updates from the IPCC’s previous assessment report in 2013 include:

1. The influence of human-driven activities on the climate system is an established fact. It is “unequivocal” that the increase of carbon dioxide, methane and nitrous oxide in the atmosphere over the industrial era is the result of human activities, and that these activities are the principal driver of many changes which have been observed across the atmosphere, ocean, cryosphere (frozen water) and biosphere.

2. Each of the last four decades has been successively warmer than any decade that preceded it since 1850. Global surface temperature was 1.09 degrees Celsius higher in 2011 to 2020 than in the period between 1850 to 1900.

3. In 2019, atmospheric carbon dioxide concentrations were higher than at any time in the last 2 million years, and concentrations of methane and nitrous oxide were higher than at any time in the last 800,000 years.

4. Human-induced climate change is already affecting a significant number of weather and climate extremes in “every region across the globe”. Many changes – particularly to the ocean, ice sheets and global sea level – are “irreversible” for centuries to millennia, due to past and future greenhouse gas emissions.

5. Under all the emissions scenarios considered in the Report, global surface temperature will continue to increase until at least the mid-century.

6. Limiting human-induced global warming to a specific level requires limiting cumulative carbon dioxide emissions, reaching at least net zero carbon dioxide emissions and significantly reducing other greenhouse gas emissions. The Report further states that “strong, rapid and sustained reductions” in methane emissions would also reduce the warming effect and would improve air quality.


The launch of the Report starkly concluded that “the climate we experience in the future depends on our decisions now”. In the planning context, the ultimate objective of sustainable development is to meet the needs of the present without compromising the needs of future generations (NPPF July 2021, paragraph 7). The IPCC Sixth Assessment Report provides further evidence of the grave extent to which development contributing to climate change endangers future generations, and the necessity for policymakers and those exercising planning judgment to contend with the impact of their decisions on the climate.

In October 2018, the IPCC’s Special Report on Global Warming of 1.5˚C described in detail the extent of dangerous climate change impact caused by warming above 1.5˚C and warned that there were 12 years in which to take action to prevent global temperature rise above that level. The Special Report had wide ramifications, sparking the Climate Emergency movement across the globe and providing the foundation for the CCC’s recommendation, in May 2019, that the UK adopt the Net Zero Obligation (ie the legal duty in the Climate Change Act 2008 to reduce greenhouse gas emissions to “at least 100%” lower than the 1990 baseline).

It will be interesting to see what the ramifications will be of the IPCC’s Sixth Assessment Report. In its Sixth Budget Report in December 2020, the CCC stated that the “2020s are the crucial decade: with effective action starting now, by 2030 the UK will be firmly on track to Net Zero.” (pg 24; see also pgs 430-433) – the IPCC’s Sixth Assessment Report reinforces that the 2020s are indeed the crucial decade in which deep emissions reductions are required, meaning that government policies, some long awaited, are urgently required to provide the policy levers, across the economy, to achieve these reductions.

In June 2020, the CCC provided two Progress Reports to Parliament, on Reducing Emissions and on Climate Adaptation. Both recommended that the Government consider options for introducing a Net Zero Test to ensure that all policies and decisions are compliant with Net Zero. The IPCC’s Sixth Assessment Report provides significant impetus for this test to be adopted. Importantly, any such test must be underpinned by clear metrics, so that both the positive and negative climate impacts of decision-making can transparently be assessed.

Link to the full IPCC Report and summary for policymakers
Watch a recording of the IPCC Report launch

Estelle Dehon is instructed in a number of matters concerning climate change, including the inquiry into the proposed new Cumbria coal mine; the inquiry considering expansion of Bristol Airport and the Court of Appeal case of Finch, which will consider the correct approach to assessing the greenhouse gas emissions of fossil fuel development.