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In the past few months, it has been hard to miss the impact that Greta Thunberg, a Swedish schoolgirl, has had on the global politics of climate change. She has inspired millions of people to join the global climate strikes and addressed world leaders at the UN General Assembly. She has attracted a huge amount of praise and support, but she has also faced a notable amount of criticism. Her way of dealing with this has been to say that her message is simple. She has called for people to unite behind the science which shows the danger that we are in from the rate of climate change. She points to the fact that it will be her and her peers who will be directly affected by the impact of climate change. What we all do now, or fail to do, to control the climate emergency, will have a huge impact on younger generations.

Extinction Rebellion (XR), a civil disobedience group campaigning to prompt action on the climate emergency has also had a major impact on the global politics of climate change. The response to XR has been similar— much praise and support, but also criticism. XR’s way of dealing with this has been to say that their message is to speak the truth and encourage others to understand the danger that we are all in from climate change. They have called for everyone to act together to prevent as much of this as is still possible.

Together these movements are strong and support for their message is growing rapidly. They are achieving a level of public participation that many of us veterans have hoped for and worked towards for the past thirty years. What they are saying is exactly what the science is at last saying. Some may ask, why at last? Hasn't the science always said this? The answer is no it hasn't.

Since the UK Climate Act was agreed in 2008, it had been asserted (wrongly) that the upper limit of 2.0° C average global warming is safe against the threat of runaway rates of climate change taking hold.
The IPCC 5th Assessment Report (AR5 published in 2015) was based on that assumption. It was the result of the largely feedback-free Representative Concentration Pathway (RCP) policy-scenarios which dominated the output of AR5 in its summary for policy makers with this aspirational limit for global temperature rise of 2.0° C.

The omission of feedback-effects is very serious, as climate models under-estimate the rates of climate change and the risks we face as a result. These omissions were denied by the UKMO in an Enquiry by the Environmental Audit Select Committee in 2013. However, these omissions were confirmed by DECC in 2016. This has been and remains a substantive issue, as does the contentious issue of the base year for temperature rise.

When the IPCC’s AR5 was published in 2015, it included the lower limit of 1.5° C average global temperature rise. This was largely the result of enormous political pressure brought in the negotiations by the nations of the Climate Vulnerable Forum.

This resulted in the IPCC commissioning a special report to establish what would be necessary to limit a global temperature rise to 1.5° C above pre-industrial levels as a lower, but safer maximum upper limit on temperature rise. This was published in August 2018.

It is behind this science that Greta Thunberg and XR are now calling for us all to unite. Preventing the global temperature rise from going 1.5° C above pre-industrial levels, requires us to achieve zero emissions globally by 2034. This is much faster than zero emissions globally by 2075, which was the rate put forward in RCP 2.5 to limit global warming to  2.0° C. It's also much  faster than reaching zero emissions globally by 2050, which is the UN’s new target and would give us a 1 in 2 chance of  for limiting temperature rise to 1.5° C. And as Wolfgang Knorr, a climate scientist recently  observed, "Professions such as doctors wouldn't take such a punt on preserving life if better odds were available."

Simply put, to resolve the accelerating problem of CO2 accumulation in the global atmosphere (at around 50% of emissions), means acting faster to prevent it than we are creating it. It means we need to be removing our CO2 emissions to the atmosphere at two, three or even four times the rate of emissions at which we are currently adding them if we are serious about limiting global temperature rises  1.5° C. Unless such steep cuts in CO2 emissions start now, the danger is that the still rising rates of emissions, concentrations, temperature and positive feedbacks to changing climate, potentially accelerate completely beyond our ability to control them in any way whatsoever.

As things stand our emissions levels are above those projected in RCP 8.5. Nature magazine pointed out  that the RCP 8.5 emissions path equals Permian Extinction levels of atmospheric CO2 concentration and temperature rise in the 21st Century. In the Permian Extinction Event, it is estimated that 95% of all life forms were made extinct.

The principle of contraction and convergence (a global framework for reducing greenhouse gas emissions to combat climate change) could be the basis on which internationally we can organize to be compliant with the United Nations Framework Convention on Climate Change Kyoto Protocol. This protocol sets internationally binding emission reduction targets.

Contraction and convergence became the basis of the UK Climate Change Act in 2008. Lord Adair Turner, the then chair of the Climate Change Committee said that if for reasons of urgency the global rate at which contracting greenhouse gas emissions had to be increased, then for reasons of equity the rate of convergence had to be accelerated relative to that.

The issue couldn't be more urgent, climate-inequity and mortality are increasing and the moment for organizing on the basis of contraction and convergence is now. The UN Secretary General recently warned again forcefully that the race against the climate crisis is a race we are all losing and that to win it demands urgent action.

A strategy for UNFCCC-Compliance needs a structure, not the rolling programme of climate-triage that will occur in the absence of that strategy. The medical profession, has expressed a remarkable degree of support for this, and has a duty to call for further action

Aubrey Meyer is one of the co-founders of the Global Commons Institute (GCI).
He has campaigned for thirty years on GCI's campaign for UNFCCC-Compliance.

Dr Robin Stott has been a medical professional for fifty years, achieving remarkable support for this programme.

No Competing interest.