What are the findings of the report United in Science?

Published: September 25, 2019

The report ‘United in Science’ prepared by the Science Advisory Group of the summit has been released ahead of the UN Climate Action Summit 2019 in New York.

Findings of the Report

  • The average global temperature for 2015-2019 is on track to be the warmest of any equivalent period on record, and July 2019 was the hottest month on record globally.
  • This warmest five-year trend has affected large areas of the United States, including Alaska, eastern parts of South America, most of Europe and the Middle East, northern Eurasia, Australia and areas of Africa south of the Sahara.
  • The greenhouse gases have reached “new highs”, heatwaves were the “deadliest” meteorological hazard in this period, and tropical cyclones led to the largest economic losses.
Global Temperature

The average global temperature for 2015-19 is currently estimated to be 1.1°C above pre-industrial (1850-1900) times. Events such as widespread and long-lasting heatwaves, record-breaking fires, tropical cyclones, floods and drought have had major impacts on socio-economic development and the environment.

Greenhouse Gases

Levels of carbon dioxide, methane and nitrous oxide have reached new highs. The report mentions that carbon dioxide concentrations are on track to reach or even exceed 410 ppm by the end of 2019. Last time Earth’s atmosphere contained 400 parts per million carbon dioxide was about 3-5 million years ago.

The growth rate of carbon dioxide 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.

The globally averaged atmospheric concentrations of carbon dioxide were 405.6 ppm, methane at 1859 parts per billion (ppb) and nitrous oxide at 329.9 ppb in 2017. These constitute 146%, 257% and 122% of pre-industrial levels (pre-1750) respectively.

The emissions from the US and the European Union have declined over the past decade and growth in China’s emissions has slowed significantly compared to the 2000s.

Indian emissions were the fourth-highest and it is growing strongly at annual rates in excess of 5%, albeit starting from a much lower base of per capita emissions.

Heatwaves

The report notes that heatwaves affected all continents and has set many new national temperature records.

2,248 deaths were reported in India, and 1,229 in Pakistan due to the heatwave which struck the Indian subcontinent in mid-2015.

The 2019 summer saw unprecedented wildfires in the Arctic region with 50 megatons of carbon dioxide emitted into the atmosphere in June alone,” the report says.

Precipitation

The effects of climate change were more pronounced on precipitation levels in the 2015-2019 period when compared to the five years preceding that.

The average precipitation totals were higher in the 2015-2019 five year period when compared to the 5 year preceding period in large regions in southern South and North America, Eastern Europe and most of Asia.

In contrast, there was less precipitation in large parts of Europe, south-west and southern Africa, northern North America and a large part of South America, the Indian Monsoon region, and northern and western Australia.

Sea Ice

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. 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.

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