Greenhouse gases surge to new highs worldwide in 2017: US report

James Marshall
August 4, 2018

Shifts in climate metrics can cause extreme weather events like heatwaves, downpours and wildfires, the report notes. Described as Earth's "annual physical", the report was co-authored by 524 authors from 65 countries, and also confirms 2017 as either the second- or third-hottest year on record ― the figures differ slightly based on which of two global data sets are used. El Niño is the warm phase of a routine sea surface temperature pattern in the tropical Pacific Ocean.

The rise in globally averaged levels of methane from 2016 to 2017 was 6.9 ± 0.9 ppb, and the mean global atmospheric nitrous oxide levels rose 0.9 ppb from 2016 to 2017.

Last year, the top three most unsafe greenhouse gases released into Earth's atmosphere - carbon dioxide, methane and nitrous oxide - reached new record highs. This is 2.2ppm greater than 2016 and is the highest level discernible in modern records, as well as ice cores that show Carbon dioxide levels back as far as 800,000 years.

The oceans are also heating up, with significant planet-altering consequences.

According to the report, ocean heat content was also at a record high, as were global sea levels in 2017.

"The 10 warmest years on record have all occurred since 1998, with the four warmest years occurring since 2014", said the report. The world's oceans are approximately 3 inches higher than they were in 1993 and are rising at an average 1.2 inches per decade, according to the findings.

"Today's abnormally warm Arctic air and sea surface temperatures have not been observed in the last 2,000 years", the report stated.

A three-year stretch to May 2017 was the "longest, most widespread and nearly certainty most destructive" coral bleaching event on record, the report states, taking a notable toll on places such as the Great Barrier Reef in Australia. The September 2017 sea ice minimum was the eighth lowest on record, 25 percent smaller than the long-term average. On March 1 it hit a record low extent since satellites began observing the ice in 1978. But one of the most important revelations in the report for the Cayman Islands is the continued sea-level rise.

The latest edition of this report was released a year after the U.S. - the world's second-largest polluter after China - withdrew from the landmark 2015 Paris climate accord, in which 170 countries committed to reductions in carbon emissions. According to the report, the total ice loss since 1980 is the equivalent to slicing 22 metres off the top of the average glacier.

"Climate is not experienced in annual averages", the report states, even though that is how we most often monitor and gauge the changes in our planet's climate variability - both natural and human-influenced.

Prolonged warmth in the seas helped spur a huge coral bleaching event, which is when coral reefs become stressed by high temperatures and expel their symbiotic algae. That can create a positive feedback loop in which warmer oceans drive a faster decline of Arctic sea ice than climate models had predicted.

Hurricane Harvey dumped record rainfall totals in Texas and Louisiana, including a new USA record of 60.5 inches (1,538 mm) which smashed the old record of 52 inches (1,320 mm).

There were several major rainfall events in 2017 contributing to a wetter than normal year, with the Indian monsoon season claiming around 800 lives and devastating floods occurring in Venezuela and Nigeria.

And fire activity was at its lowest globally since at least 2003 - but the USA had by far its most expensive fire season ever, with more than $18 billion in damages. Just to the north, Canada's British Columbia saw 1.2 million hectares burn during their driest summer on record.

Other reports by Click Lancashire

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