The Guardian • Issue #1974

UN IPCC Report

No time to waste – Part one

“Climate change is already affecting every inhabited region across the globe with human influence contributing to many observed changes in weather and climate extremes.”

“Some of the changes are irreversible.”

“It is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred.”

These are amongst the sobering findings of the Sixth Assessment Report (6AR) of the United Nations Intergovernmental Panel on Climate Change (UN IPCC) that was released on Monday, 9th August. 234 leading scientists from around the world, including from Australia, synthesised 14,000 research papers as the basis of this, the sixth such report, the last one being in 2013.

While 6AR paints an alarming picture of global warning, at the same time it offers hope of avoiding catastrophic changes if radical and swift action is taken. However, its purpose is not to make recommendations on what needs to be done. Policy is the responsibility of governments.

The 6AR will play an important role at the 26th session of the Conference of the Parties (COP 26) to the UN Framework Convention on Climate Change in Glasgow in November.

Article 2 of the Paris Agreement (COP25) committed nations to: “Holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels […]” But pledges under the Paris Agreement will only take global warming to 3°C-5°C.

The world hangs on a precipice, with the future of humanity and life as we know it at stake. Much more will be required at COP26.

The 6AR is in four parts. The report released last week is the first. It focuses on the physical science of the basis of climate change. The second, to be released in 2022, will cover the impacts, adaptation, and vulnerability of people, ecosystems, agriculture, and cities. It will be followed by one on the economics and mitigation of climate change. The final report, due in September 2022, will be a synthesis of the first three.


It did not need a scientific report by eminent scientists to realise climate change is already upon us. Witness the floods in Europe and China; fires in North America, Europe, and Australia; rising acidity of oceans; melting ice caps and glaciers; drought and desertification; and all the other extreme weather events. They will become more frequent and intense. The devastating impacts on farming, health, fresh water, air pollution, and ecosystems, are already being felt globally. Millions of people are being displaced by rising oceans and other consequences of climate change.

The changes that we are experiencing now are a forewarning of much worse to come and make 6AR a compelling read as to the global urgency of the situation. The scientific findings must not be ignored.

The UN IPCC updates previous forecasts, warning global warming could reach 1.5C above pre-industrial levels by 2030, ten years earlier than previously noted in its 2013 report. The global mean temperature rise since the pre-industrial period is already at 1.1°C.

The speed and magnitude of change brought about by humans is difficult to imagine. A couple of quotes to illustrate this:

“The scale of recent changes across the climate system as a whole and the present state of many aspects of the climate system are unprecedented over many centuries to many thousands of years.”

“In 2019, atmospheric CO2 concentrations were higher than at any time in at least 2 million years (high confidence), and concentrations of CH4 [methane] and N2O [nitrous oxide] were higher than at any time in at least 800,000 years (very high confidence).”

“Global warming of 1.5°C and 2°C will be exceeded during the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades.”

“Many changes in the climate system become larger in direct relation to increasing global warming. They include increases in the frequency and intensity of hot extremes, marine heatwaves, and heavy precipitation, agricultural and ecological droughts in some regions, and proportion of intense tropical cyclones, as well as reductions in Arctic Sea ice, snow cover and permafrost.”

The increase in greenhouse gases and consequential changes have already set in train ongoing changes. For example: “Mountain and polar glaciers are committed to continue melting for decades or centuries (very high confidence). Loss of permafrost carbon following permafrost thaw is irreversible at centennial timescales (high confidence). Continued ice loss over the 21st century is virtually certain for the Greenland Ice Sheet and likely for the Antarctic Ice Sheet. There is high confidence that total ice loss from the Greenland Ice Sheet will increase with cumulative emissions.” (Italics in the original)


Taking a physical science perspective, the 6AR notes three requirements to limiting human-induced warming to a specific level:

  • limiting cumulative CO2 emission
  • reaching at least net zero CO2 emission
  • strong reductions in other greenhouse gas emissions.

The first of these is a critical factor which developed countries, corporations, and the mass media conveniently overlook. If global warming is to be limited to 1.5°C or the upper limit of 2°C, then the total of accumulated emissions must be taken into consideration as well as ongoing new emissions. These two separate factors are critical to policy formulation. It is NOT enough to talk about zero-net emissions.

The carbon budget takes into consideration the existing accumulation of greenhouse gases and calculates the additional cumulative emissions that would restrict the temperature rise to a specific level. The IPCC Special Report on 1.5°C warming (SR1.5) estimates the remaining carbon budget from 2018 onwards is 480 gigatonnes (billion tonnes or Gt) of carbon dioxide equivalent (GtCO2eq), for a 50 per cent probability of restricting temperature rise to less than 1.5°C. At the current rate that budget would be depleted in twelve years.

There is also an equity factor to take into consideration. Article 4.1 Paris Agreement states: “[…] Parties aim to reach global peaking of greenhouse gas emissions as soon as possible, recognising that peaking will take longer for developing country Parties [… and] on the basis of equity, and in the context of sustainable development and efforts to eradicate poverty.”

Limiting global warming to 1.5°C requires the sharing of the remaining carbon budget in an equitable manner.

Developed countries must not only meet zero targets by 2030, but strive for negative net emissions, if the 1.5°C aim is to be met. They are responsible for most of the accumulated emissions and have a moral responsibility to contribute on an equitable basis.

Part 2 next week: Australia’s role and the way forward.

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