United Science report on Climate
The world’s leading climate science organizations have joined forces to produce a landmark new report for the United Nations Climate Action Summit, underlining the glaring – and growing gaps – between agreed targets to tackle global warming and the actual reality.
The report, United in Science, includes details on the state of the climate and presents trends in the emissions and atmospheric concentrations of main greenhouse gases. It highlights the urgency of fundamental socio-economic transformation in key sectors such as land use and energy in order to avert dangerous global temperature increase with potentially irreversible impacts. It also examines tools to support both mitigation and adaptation.
“The Report provides a unified assessment of the state of our Earth system under the increasing influence of anthropogenic climate change, of humanity’s response thus far and of the far-reaching changes that science projects for our global climate in the future. The scientific data and findings presented in the report represent the very latest authoritative information on these topics,” said the Science Advisory Group, which is co-chaired by WMO Secretary-General Petteri Taalas and Leena Srivastava, outgoing Vice Chancellor of TERI School of Advanced Studies.
Highlights from the report include:
The Global Climate in 2015-2019 (World Meteorological Organization, WMO):
Warmest five-year period on record
The average global temperature for 2015–2019 is on track to be the warmest of any equivalent period on record. It is currently estimated to be 1.1°Celsius (± 0.1°C) above pre-industrial (1850–1900) times. Widespread and long-lasting heatwaves, record-breaking fires and other devastating events such as tropical cyclones, floods and drought have had major impacts on socio-economic development and the environment.
Continued decrease of sea ice and ice mass
Arctic summer sea-ice extent has declined at a rate of approximately 12% per decade during 1979-2018. The four lowest values for winter sea-ice extent occurred between 2015 and 2019.
Overall, the amount of ice lost annually from the Antarctic ice sheet increased at least six-fold between 1979 and 2017. Glacier mass loss for 2015-2019 is the highest for any five-year period on record.
Sea-level rise is accelerating, sea water is becoming more acid
The observed rate of global mean sea-level rise accelerated from 3.04 millimeters per year (mm/yr) during the period 1997–2006 to approximately 4mm/yr during the period 2007–2016. This is due to the increased rate of ocean warming and melting of the Greenland and West Antarctica ice sheets. There has been an overall increase of 26% in ocean acidity since the beginning of the industrial era.
Record Greenhouse Gas Concentrations in the Atmosphere
WMO Global Atmosphere Watch
Levels of the main long-lived greenhouse gases, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) have reached new highs.
The last time Earth’s atmosphere contained 400 parts per million CO2 was about 3-5 million years ago, when global mean surface temperatures were 2-3°C warmer than today, ice sheets in Greenland and West Antarctica melted, parts of East Antarctica ice had retreated, all causing global see level rise of 10-20m compared with today.
In 2018, global CO2 concentration was 407.8 parts per million (ppm), 2.2 ppm higher than 2017. Preliminary data from a subset of greenhouse gas monitoring sites for 2019 indicate that CO2 concentrations are on track to reach or even exceed 410 parts per million (ppm) by the end of 2019.
In 2017, globally averaged atmospheric concentrations of CO2 were 405.6 ±0.1 ppm, CH4 at 1859 ±2 parts per billion (ppb) and N2O at 329.9 ±0.1 ppb. These values constitute, respectively, 146%, 257% and 122% of pre-industrial levels (pre-1750).
The growth rate of CO2 averaged over three consecutive decades (1985–1995, 1995–2005 and 2005–2015) increased from 1.42 ppm/yr to 1.86 ppm/yr and to 2.06 ppm/yr