IPCC Climate Report

On Monday after a yearlong delay due to covid, the U.N.  Intergovernmental Panel on Climate Change(IPCC) released the first report on Climate Change since 2013. The report, issued by the IPCC’s Working Group I and approved by 195 member governments, is the first in a series leading up to the 2022 IPCC Sixth Assessment Report and serves as a motivational leadoff to the 26th UN Climate Change Conference of the Parties (COP26) in Glasgow on October 31, 2021-November 12, 2021.

Since the IPCC report is based on previously published peer reviewed work there were no surprises. (I will admit that I only read the Summary for Policymakers and sections of the discussion on the climate models in key findings.) Climate change is widespread and intensifying. The concentration of greenhouse gases in the atmosphere is at its highest level since the dawn of mankind. Before the COVID-19 pandemic when the data set used stops, emissions of carbon dioxide had been rising by about 1% per year on average for the past decade. Renewable energy use has been expanding rapidly, but much of the renewable energy is being deployed alongside existing fossil energy, not replacing it.  All the climate models tie the rise in temperature to concentrations of atmospheric carbon dioxide. The planet has warmed 1.1 degrees C since the late 19th century and is expected to warm an additional 0.4 degrees C in the next 20 years.

“At 1.5°C global warming, heavy precipitation and associated flooding are projected to intensify and be more frequent in most regions in Africa and Asia (high confidence), North America (medium to high confidence) and Europe (medium confidence). Also, more frequent and/or severe agricultural and ecological droughts are projected in a few regions in all continents except Asia.”

From IPCC

Mankind in their burning of fossil fuels and covering the earth with concrete is responsible for this rise in temperature. No actions that nations can likely agree to take at November’s COP26 meeting can change this trajectory we only have some hope of moderating it.  That is the key finding of the latest scientific report from the IPCC. Scientists use the five projection scenarios to demonstrate the difference that our coordinated action can make, but also warn: “The magnitude of feedbacks between climate change and the carbon cycle becomes larger but also more uncertain in high CO2 emissions scenarios (very high confidence). However, climate model projections show that the uncertainties in atmospheric CO2 concentrations by 2100 are dominated by the differences between emissions scenarios (high confidence). Additional ecosystem responses to warming not yet fully included in climate models, such as CO2 and CH4 fluxes from wetlands, permafrost thaw and wildfires, would further increase concentrations of these gases in the atmosphere (high confidence).”

The IPCC report finds that changes in the Earth’s climate in every region and across the whole climate system have occurred and are resulting in increase in extreme weather events. “In 2019, atmospheric CO2 concentrations were higher than at any time in at least 2 million years (high confidence), and concentrations of CH4 and N2O were higher than at any time in at least 800,000 years (very high confidence).” “Global surface temperature has increased faster since 1970 than in any other 50-year period over at least the last 2000 years (high confidence).”

Recent work had shown an oversensitivity of the climate models to changes in CO2 levels; however, the actual warming of the earth has gone on long enough to identify the inconsistency and the to constrain their projections somewhat. Nonetheless, the report finds the forecast warmer climate will intensify weather events and the resulting flooding or droughts; but the location and frequency of these events depend on projected changes in regional atmospheric circulation, including monsoons and mid-latitude storm tracks and cannot be projected at this time.

It is virtually certain that global mean sea level will continue to rise over the 21st century. Long term “sea level is committed to rise for centuries to millennia due to continuing deep ocean warming and ice sheet melt, and will remain elevated for thousands of years (high confidence).”

“Limiting human-induced global warming to a specific level requires limiting cumulative CO2 emissions, reaching at least net zero CO2 emissions, along with strong reductions in other greenhouse gas emissions. Strong, rapid and sustained reductions in CH4 emissions would also limit the warming effect resulting from declining aerosol pollution and would improve air quality.” There are the marching orders for COP26 in Glasgow this fall. Good luck to us all.