The Intergovernmental Panel on Climate Change (IPCC) has released its latest assessment of the physical science of global warming. It warns that countries must cut greenhouse gas emissions quickly and sharply, to avoid the most dangerous consequences of climate change. There is still time to limit average global warming to 1.5°C, but nations must act now. CDKN's Mairi Dupar reports. The extent of extreme weather, in just the past year and a half, has been shocking: dangerous wildfires held large swathes of Australia, the western United States and Greece in their grip. Deadly floods shook Germany and central Europe and China. Super-Cyclone Amphan slammed into India and Bangladesh; then Super-Typhoon Goni hit the Philippines months later. Heatwaves are breaking records. For the hundreds of millions of people around the world recently affected by these extremes, the message that the planet is heating up and climate change is to blame is no surprise. But for the Intergovernmental Panel on Climate Change (IPCC) to confirm this message, in stronger and more definitive language than ever before, carries a special weight. The IPCC has today launched Climate Change 2021: The Physical Science Basis, which makes up part of its Sixth Assessment Report. Today’s report examines changes in temperatures and rainfall in the past, present and future. It tells how the oceans expand as they heat; how global warming melts ice sheets, glaciers and other frozen parts of the Earth’s surface; and how these changes are driving increasing rates of sea level rise. The report draws on major advances in climate science since the last assessment was published in 2013-14, to establish, more robustly, how human-made emissions contribute to extreme weather events. The report makes it clear that we still have a choice: to cut carbon dioxide emissions to net zero by 2050 and curb other greenhouse gases very fast. This could limit global warming to 1.5°C over the course of this century, and so limit the impacts of climate change on the environment and people. If we permit higher emissions, we may face a climate above 2°C in which many jobs, homes and infrastructure, food and water supplies are dangerously insecure. The IPCC’s report is based on the review, by 234 authors, of more than 14,000 scientific publications. The Summary for Policy Makers has been approved by governments from around the world. Today’s report ought to send political reverberations through the forthcoming global climate change talks, COP26, in Glasgow. The talks urgently need to be re-invigorated, after their Covid-related postponement from 2020. The report could provide the scientific impetus that is needed. Why today’s report is important The previous IPCC assessment, the Fifth Assessment Report (2013-14) found it ‘extremely likely’ that greenhouse gas emissions from human activity were contributing to global warming; but today’s report says ‘it is unequivocal that human influence has warmed the atmosphere, ocean and land’. Average global surface temperatures were 1.09°C higher in 2011-20 than in pre-industrial times (1850-1900). But this is a global average - individual countries and regions have experienced higher average temperature rises (like Namibia, for instance, a ‘hotspot’). There is now robust scientific evidence to show that heat extremes, heavy precipitation and droughts are increasing in frequency across every region of the world - as shown in the IPCC’s online interactive atlas. A range of scenarios The Physical Science Basis report describes five different greenhouse gas emission scenarios, associated with warming from 1.5°C to 4.4°C (above pre-industrial levels) this century. Even the very lowest greenhouse gas emission scenario considered by the IPCC would more likely than not see average global temperatures rise to 1.6°C by mid-century (called ‘overshoot’) before settling toward 1.4°C by the end of the century. With each additional increment in global warming, extreme weather events become more extreme. The IPCC finds, for example, “every additional 0.5°C of global warming causes clearly discernible increases in the intensity and frequency of hot extremes, including heatwaves (very likely), and heavy precipitation (high confidence), as well as agricultural and ecological droughts in some regions (high confidence).” Figure: Five IPCC scenarios (associated with low emissions pathways (SSP1.-1.9) to high emissions pathways (SSP5-8.5). Source: Climate Change 2021: The Physical Science Basis. We cannot take for granted, either, the ability of Earth’s natural systems to simply absorb our pollution. The greater carbon dioxide emissions are, the less effective the Earth’s oceans and lands will become at storing or taking up excess carbon (this includes our forests, grasslands and wetlands, and soils more generally). With higher levels of emissions, our ecosystems’ ability to buffer our actions diminishes. The IPCC’s report also alerts us to the possibility of low-likelihood events that could be set in train by human-induced climate change this century, which would have devastating consequences. These include the potential for massive sea level rise (see diagram) under a high emissions scenario.  Hundreds of millions of people live on land less than 2 metres above sea level, the majority of them in the tropics. Figure: There is a direct correspondence between high levels of greenhouse gas emissions from human activity this century (SSP5-8.5) and the extent of sea level rise this century, with there being a possibility - although of low probability - of hugely destructive changes under the highest emissions scenario. Source: Climate Change 2021: The Physical Science Basis. What’s needed next: stronger climate plans, more finance These alarming findings will shake political leaders to the core - especially those from atoll nations and other Small Island Developing States (SIDS), who have adopted the rallying cry ‘1.5 to stay alive’. The high sea levels, as well as high temperatures and droughts associated with more than 1.5°C of global warming are considered a critical risk to their viability as nations. SIDS and Least Developed Countries (LDCs) suffering the worst consequences of climate change, and with the least role causing it, will have good reason to use today’s report to reinforce their calls for a halt to fossil fuel investments. As UN Environment Programme Director Inger Andersen noted at today's launch event, the G20 countries are responsible for the vast majority (78%) of today’s greenhouse gas emissions. However, several G20 members (such as China, India, Saudi Arabia and South Africa) are still to submit their new or updated 2020 climate action plans, known as the NDCs, to the United Nations. Meanwhile, Climate Tracker finds that some updated NDCs are lacking in adequate ambition. SIDS and LDCs will also have reason to redouble their calls for much increased donor funding for low-carbon development at home and abroad, finance for climate adaptation, and compensation for climate-related loss and damage. Many climate-smart development choices are cost-competitive with fossil fuels or even cheaper, in today’s markets (such as renewable energy technologies). However, switching out of fossil-fuel dependency into low-carbon alternatives and paying the bill for climate-resilient housing and infrastructure can add costs to policies and projects. Many low- and middle-income countries have struggled to integrate these costs adequately into budgets, especially in light of Covid-related disruption. In this context, financing for development that is compatible with the Paris Agreement’s 1.5°C global temperature goal has never been a more pressing concern. Rich nations have not yet met their 2020 target to disburse $100 billion of climate finance each year to low- and middle-income countries to finance climate-smart development. Today's IPCC report is a reminder that the finance must urgently be released. A new, more ambitious global goal for climate finance should be set and met, to catalyse the needed changes to avert a deeper planetary emergency. Ambassador Diann Black-Layne, Lead Climate Negotiator for the Alliance of Small Island States (AOSIS) has stressed today that the “fossil fuel sector... is being paid annual subsidies of over $600 billion to destroy our planet, while the UN Climate Fund gets US $2.4 billion a year to save it. We have to turn this around.”  Prime Minister Gaston Browne of Antigua and Barbuda, AOSIS Chair, has said “we need our developmental partners to fulfil their commitments and formulate a new global financial goal commensurate with the new global realities.” “We need to see developed countries and large emitters take the lead and slash emissions, and we need the assurance that this will happen urgently,” said H.E. Sonam P Wangdi, Chair of the LDC Group of climate negotiators - in response to the IPCC report. “More ambitious NDCs that close the emissions gap must be submitted by COP26. Resubmitting the same NDC is not enough – we clearly need stronger emissions reduction targets for 2030. We really are running out of time.” The IPCC is a scientific body, not a political one. But its conclusions today are deeply politically relevant. They lead directly to conversations about money, policy, and society-wide commitment to change.   Image: Mozambique in the aftermath of Cyclone Idai (courtesy Red Cross Climate Centre)