It is unequivocal. Climate change is driven by us

The International Panel on Climate Change’s (IPCC) Sixth Assessment Report (AR6), released last night Australian time highlighted that “it is unequivocal that human influence has warmed the atmosphere, ocean, and land.” The report makes it clear that climate change is affecting every continent, region, and ocean on earth, along with every facet of the weather and that escape from its impacts is no longer possible, only mitigation and the chance to avoid its worst effects.

This report is the cumulative output of five years of work, involving 234 authors from 66 countries, 78,007 review comments, and over 14,000 cited research papers.

What is AR 6?

Every five years (or so) the IPCC publishes an updated assessment of climate change in three parts (plus a summary). Assessment Report 6 (AR6) is the latest series or assessment. Climate Change 2021 – the Physical Science Basis’ is the first part to be released. Parts two and three will look at Impacts, Adaptation and Vulnerability (Feb 2022) and Mitigation (March 2022) respectively. The Physical Science report centres on the projected impacts of five emissions scenarios, while the second and third reports will look at how to adapt to these impacts and ultimately how to prevent the worst-case scenarios.

What are the five scenarios?

Within AR6, the five scenarios called Shared Socioeconomic Pathway (SSP) include;

SSP1-1.9Our best-case scenario and is the only one that meets the Paris Agreement’s goal of keeping global warming to around 1.5 °C above pre-industrial temperatures

SSP1-2.6Within this scenario, net-zero emissions are reached after 2050, with temperatures stabilising around 1.8°C higher by the end of the century.

SSP2-4.5 – Under this scenario CO2 emissions are maintained around current levels before starting to fall mid-century but do not reach net-zero by 2100 with temperatures rising by 2.7°C by the end of the century.

SSP3-7.0 – On this path, emissions and temperatures rise steadily, and CO2 emissions roughly double from current levels by 2100. By the end of the century, average temperatures have increased by 3.6°C.

SSP5-8.5 – Considered a worst-case scenario, where current CO2 emissions levels roughly double by 2050 and by 2100, the average global temperature is a scorching 4.4°C higher.

Each SSP reference refers the socio-economic scenario number and the particular physical level of CO2 concentration (known as a Regional Concentration Pathway or RCP).

What is clear is that in every scenario, worsening climatic impacts will be found and, temperature rises are assured.

Key findings:

While there are many significant conclusions and observations made in AR6, the following findings stand out:

  • Human influence has warmed the climate at an unprecedented rate over the last 2000 years, with surface temperatures being 1.09°C higher in 2011– 2020 than 1850–1900.
  • Simulations indicate that the 1.5-degree mark may be exceeded between 2025 and 2037 under specific scenarios.
  • There is now a ‘high confidence’ that human activities are the main drivers of more frequent or intense heatwaves, glaciers melting, ocean warming, and ocean acidification.
  • We have reached tipping points where experienced impacts are irreversible for centuries to millennia, especially changes in the ocean temperatures and acidification, ice sheet reductions, and global sea level rises. Other tipping points such as the thawing of permafrost are expected to be reached with ‘high confidence’
  • To maintain a 50% chance of meeting the goals of the Paris agreement, there is a total carbon budget of 500 billion tonnes of CO₂. At current rates of emissions, this will be exhausted within 12 years.
  • For Australia, there is high confidence that the occurrence of droughts, extreme fire weather, and rainfall variability are going to increase.

What’s next?

The findings from this IPCC report are frightening. However, we should not lose sight of recent global progress. We have seen significant steps taken in net-zero commitments by countries and companies, investors successfully imposing their influence through shareholder resolutions and accountability and consequences beginning to materialise as a cost for inaction in the court room. As a result, climate change is firmly on the agenda for companies and their shareholders.

AR6 does tell us (with greater certainty than ever before) what happens under certain conditions, but AR6 does not predict our future. This report does not tell us which scenario is most likely. Our decisions as individuals, companies and governments will decide the outcome. At its core, limiting warming to the lowest possible level needs to a fundamental focus in everything we do: there is a direct relationship in that every bit of global warming we avoid, we will reduce the climate risks we face.

While confronting, this report highlights the critical importance of COP26 as the immediate opportunity to create more meaningful climate action towards decarbonisation.

What this report does clearly say is that time is running out and decisive action is needed now to avert the climate emergency.



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