The findings in three major documents will guide the decisions of world leaders at COP26 in Glasgow in tackling runaway climate change. World’s leaders are gathering in Glasgow to try and tighten their emission-curbing commitments with a view to reaching net zero emissions by 2050. The essential science that will guide their discussions comes from three major documents. The first – the 6th assessment of the United Nations’ Intergovernmental Panel on Climate Change (IPCC) published on August 9 – expresses greater scientific certainty than previous reports that human activity is responsible for global warming. “It is unequivocal that human influence has warmed the atmosphere, ocean and land,” it states. Several key findings back up this claim. In 2019, atmospheric carbon dioxide (CO2) concentrations were higher than at any time in at least two million years, and concentrations of methane (CH4) higher than at any time in the past 800,000 years. These concentrations “far exceed … the natural multi-millennial changes between glacial and interglacial periods over at least the past 800,000 years”, the report says. The observed increases in these greenhouse gas concentrations are specially marked after 1750, which marks the start of the Industrial Revolution in Europe. Atmospheric CO2 has increased by 47 percent since then, to reach 410 parts per million. Methane concentrations (1,866 parts per billion) have risen by 156 percent over the same period. The IPCC believes this establishes beyond doubt that greenhouse gas concentrations are unequivocally caused by human activities. More recent weather data also back up the claim that humanity is responsible for global warming. Each of the last four decades has been successively warmer than any decade that preceded it since 1850, the IPCC says. The global surface temperature was on average 1.09 degrees Celsius (1.96 degrees Fahrenheit) higher in the last decade if compared with the second half of the 19th century. Governments are underfinancing the clean energy revolution, providing one-third of the money they should be spending to meet a net zero scenario [John Psaropoulos/Al Jazeera] Rising sea levels are also an indicator of warming. The global average sea level increased by 20cm (7.9 inches) between 1901 and 2018, says the IPCC’s report. It is “virtually certain” that human-caused CO2 emissions are the main driver of the current global acidification of the surface open ocean. What will happen if leaders fail to make commitments and implement them? The IPCC modelled five emissions scenarios. If the world emulates the European Union’s commitment to halving emissions by 2030 and eliminating them altogether by 2050, possibly extracting some CO2 from the atmosphere thereafter, global average temperatures by 2100 will be roughly 1.4C (2.5F) higher than in 1850 – only slightly higher than today’s. If emissions remain at today’s levels, the global mean temperature by 2100 will be closer to 2C (3.6F) higher than in 1850. An intermediate model suggests a continued but not precipitous change in emissions, resulting in the global mean temperature increase of 2.7C (4.86F) by 2100. In the highest two models, if emissions roughly double relative to today’s, global mean temperatures by 2100 rise by between 3.6C (6.48F) and 5.7C (10.26F). So how likely is the world to follow a policy of achieving net zero emissions by 2050? Fragile wetlands are especially vulnerable to coastal flooding because of rising sea levels [John Psaropoulos/Al Jazeera] ‘Low emissions revolution’ In its latest World Energy Outlook 2021, the second crucial document, the International Energy Agency (IEA) does not see a path to net zero emissions by 2050 under the world’s announced policies, . . . read the full article here.