There are only a few weeks to go until international and local leaders from states, regions, cities, businesses, investors and civil society take up the invitation of California’s Governor Brown to attend the Global Climate Action Summit in San Francisco. The summit aims at bringing together these stakeholders – also known as non-party stakeholders or non-state actors in the climate negotiation jargon – with national government leaders to create a new wave of mobilisation. Those going to San Francisco should be sure to bring more than flowers in their hair. What is needed is a really ambitious action at the summit.

The year 2018 can be considered a midway between 2015 – when the Paris Agreement was adopted – and the year 2020 after the results of the Talanoa Dialogue need to be translated into more ambitious action. 2020 is also often considered as the critical threshold that represents the point of no return, the year until which emissions need to peak to avoid incalculable risks to humanity. The 2018-summer has already given more than a wake up-call for international politics. Devastating forest fires in places such as California, Greece and Sweden are a current example for what is now referred to as “Hothouse Earth”. This is the description given by leading scientist Will Steffen from the Stockholm Resilience Centre in a recent edition of the Proceedings of the National Academy of Sciences (PNAS). Steffen’s team warn that even if the carbon emission reductions called for in the Paris Agreement are met, earth is at risk of entering a situation of extreme conditions, i.e. a hothouse. The global average temperature would be 4-5°C higher than pre-industrial temperatures leading, for example, to a sea level 10-60 m higher than today.

Such scenarios should alert political leaders around the world, U.S. president Donald Trump among them. Right before the start of this year’s hurricane season in the Caribbean region, political leaders asked the U.S. president to revise his climate (non-)strategy and to start addressing the existential threat they face, including those from extreme weather events. Last year’s Hurricane Maria caused an ongoing disaster in Puerto Rico with thousands of casualties.

The hothouse world will be one affecting regional security and stability – accordingly this topic will be discussed in San Francisco. In a recent blog post, Ken Alex, Senior Policy Advisor to Governor Brown, stressed that the Summit will seek “to engage people who have remained on the side-lines” by really showcasing climate action around the world and presenting new commitments as well. Scientist Will Steffen and his colleagues emphasized in their PNAS study that ambitious mitigation measures must also be underpinned by fundamental societal changes to maintain a stable Earth. They also provide recommendations for enhancing or creating new biological carbon stores.

Climate diplomats need do their part in San Francisco to implement the necessary policies recommended by the scientific world.