United in Science 2021
A multi-organization high-level compilation of the latest climate science information
Key points
Greenhouse Gas Concentrations in the Atmosphere
Global Atmosphere Watch/WMO
This image shows a sample of abnormal methane concentrations over 2019 as measured by Sentinel-5P. The size and colour of the circles indicate the size and intensity of the plume detected. The redder the colour, the higher the concentration of the methane plume. This image contains modified Copernicus Sentinel data (2019), processed by Kayrros.
Global GHG Emissions and Budgets
Global Carbon Budget – GCP
Mean global N₂O budget for all major anthropogenic and natural sources and sinks for the decade 2007–2016 (redrawn from Tian et al., 2020).
Global Climate in 2017–2021
WMO
2017-2021 five-year average temperature anomalies relative to the 1981-2010 Sea ice average. Data is from NASA GISTEMP v4. Date updated to July 2021.
Highlights of IPCC Climate Change 2021 - The Physical Science Basis for the Current State of Climate
IPCC
Taken from IPCC AR6 WG1 Figure SPM.2: Assessed contributions to observed warming in 2010–2019 relative to 1850–1900. Panel a): Observed global warming (increase in global surface temperature) and its very likely range Panel b): Evidence from attribution studies, which synthesize information from climate models and observations. The panel shows temperature change attributed to total human influence, changes in well-mixed greenhouse gas concentrations, other human drivers due to aerosols, ozone and land-use change (land-use reflectance), solar and volcanic drivers, and internal climate variability. Whiskers show likely ranges {3.3.1}. Panel c): Evidence from the assessment of radiative forcing and climate sensitivity. The panel shows temperature changes from individual components of human influence, including emissions of greenhouse gases, aerosols and their precursors; land-use changes (land-use reflectance and irrigation); and aviation contrails. Whiskers show very likely ranges. Estimates account for both direct emissions into the atmosphere and their effect, if any, on other climate drivers. For aerosols, both direct (through radiation) and indirect (through interactions with clouds) effects are considered.{6.4.2, 7.3}
Heatwaves, Wildfires, and Air Pollution: Compounding and Cascading Climate Hazards to Health
WHO/WMO
COVID-19 recovery efforts should be aligned with national climate change and air quality strategies to reduce risks from compounding and cascading climate hazards, and gain health co-benefits.
Change in the average number of days per year each person was exposed to very high or extremely high wildfire risk in 2016–2019 compared to 2001–2004. Adapted from Watts et al. 2020.
Sea- level and Coastal Impacts
WCRP (WMO/IOC/ISC)
Global mean sea levels rose 20 cm from 1900 to 2018 and at an accelerated rate of 3.7+0.5 mm/yr from 2006 to 2018.
Even if emissions are reduced to limit warming to well below 2 °C, global mean sea level would likely rise by 0.3–0.6 m by 2100, and could rise 0.3–3.1 m by 2300.
Adaptation to this residual rise will be essential – adaptation strategies are needed where they do not exist – especially in low-lying coasts, small islands, deltas and coastal cities.
Scheme of the climate and non-climate driven processes that can influence global, regional (green colours), relative and extreme sea-level events (red colours) along coasts. Major ice processes are shown in purple and general terms in black. SLE stands for Sea Level Equivalent and reflects the increase in GMSL if the mentioned ice mass is melted completely and added to the ocean. [reproduction of Figure 4.4 in Oppenheimer et al., 2019] (GMSL – Global Mean Sea Level; GIA – Glacial Isostatic Adjustment.)
Global Climate in 2021–2025 – WMO Global Annual to Decadal Climate Update
Met Office/WMO/WCRP
Annual global mean near-surface temperature is likely to be at least 1 °C warmer than pre-industrial levels (defined as the 1850–1900 average) in each of the coming five years and is very likely to be within the range 0.9 °C to 1.8 °C.
Over 2021–2025, high latitude regions and the Sahel are likely to be wetter than the recent past.
There is a 40% chance that average global temperature in one of the next five years will be at least 1.5 °C warmer than pre-industrial levels but it is very unlikely (~10%) that the 5-year mean temperature for 2021–2025 will be 1.5 °C warmer than pre-industrial levels.
Emissions Gap
United Nations Environment Programme – UNEP
Five years after the adoption of the Paris Agreement, the emissions gap is as large as ever: global emissions need to be 15 GtCO₂e lower than current unconditional Nationally Determined Contributions (NDCs) imply for a 2 °C goal, and 32 GtCO₂e lower for the 1.5 °C goal.
Global GHG emissions under different scenarios and the emissions gap in 2030 (median and 10th to 90th percentile range; based on the pre-COVID-19 current policies scenario), UNEP Emissions Gap report 2020.
The COVID-19 crisis offers only a short-term reduction in global emissions. It will not significantly reduce emissions by 2030 unless countries pursue an economic recovery that incorporates strong decarbonization.
The increasing number of countries committing to net-zero emission goals is encouraging, with about 63% of global emissions now covered by such goals. However, to remain feasible and credible, these goals urgently need to be reflected in near-term policy and in significantly more ambitious NDCs for the period to 2030.
📖: Read the full report here .
