What difference has six years made?
Take a look:
ABSTRACT—J. BLUNDEN AND D. S. ARNDT
In 2018, the dominant greenhouse gases released into
Earth’s atmosphere—carbon dioxide, methane, and nitrous
oxide—continued their increase. The annual global average
carbon dioxide concentration at Earth’s surface was 407.4 ±
0.1 ppm, the highest in the modern instrumental record and
in ice core records dating back 800 000 years. Combined,
greenhouse gases and several halogenated gases contribute
just over 3 W m−2 to radiative forcing and represent a nearly
43% increase since 1990. Carbon dioxide is responsible for
about 65% of this radiative forcing.
With a weak La Niña in early 2018 transitioning to a weak
El Niño by the year’s end, the global surface (land and ocean)
temperature was the fourth highest on record, with only
2015 through 2017 being warmer. Several European countries
reported record high annual temperatures. There were also
more high, and fewer low, temperature extremes than in
nearly all of the 68-year extremes record. Madagascar recorded a record daily temperature of 40.5°C in Morondava
in March, while South Korea set its record high of 41.0°C in
August in Hongcheon. Nawabshah, Pakistan, recorded its
highest temperature of 50.2°C, which may be a new daily
world record for April. Globally, the annual lower troposphere
temperature was third to seventh highest, depending on the
dataset analyzed. The lower stratospheric temperature was
approximately fifth lowest.
The 2018 Arctic land surface temperature was 1.2°C above
the 1981–2010 average, tying for third highest in the 118-year
record, following 2016 and 2017. June’s Arctic snow cover
extent was almost half of what it was 35 years ago. Across
Greenland, however, regional summer temperatures were
generally below or near average. Additionally, a satellite
survey of 47 glaciers in Greenland indicated a net increase in
area for the first time since records began in 1999. Increasing
permafrost temperatures were reported at most observation
sites in the Arctic, with the overall increase of 0.1°–0.2°C
between 2017 and 2018 being comparable to the highest rate
of warming ever observed in the region.
On 17 March, Arctic sea ice extent marked the second
smallest annual maximum in the 38-year record, larger than
only 2017. The minimum extent in 2018 was reached on 19
September and again on 23 September, tying 2008 and 2010
for the sixth lowest extent on record. The 23 September
date tied 1997 as the latest sea ice minimum date on record.
First-year ice now dominates the ice cover, comprising 77% of
the March 2018 ice pack compared to 55% during the 1980s.
Because thinner, younger ice is more vulnerable to melting
out in summer, this shift in sea ice age has contributed to the
decreasing trend in minimum ice extent. Regionally, Bering Sea
ice extent was at record lows for almost the entire 2017/18
ice season.
For the Antarctic continent as a whole, 2018 was warmer
than average. On the highest points of the Antarctic Plateau,
the automatic weather station Relay (74°S) broke or tied
six monthly temperature records throughout the year, with
August breaking its record by nearly 8°C. However, cool conditions in the western Bellingshausen Sea and Amundsen Sea
sector contributed to a low melt season overall for 2017/18.
High SSTs contributed to low summer sea ice extent in the
Ross and Weddell Seas in 2018, underpinning the second
lowest Antarctic summer minimum sea ice extent on record.
Despite conducive conditions for its formation, the ozone hole
at its maximum extent in September was near the 2000–18
mean, likely due to an ongoing slow decline in stratospheric
chlorine monoxide concentration.
Across the oceans, globally-averaged SST decreased slightly
since the record El Niño year of 2016 but was still far above
the climatological mean. On average, SST is increasing at a rate
of 0.10° ± 0.01°C decade−1 since 1950. The warming appeared
largest in the tropical Indian Ocean and smallest in the North
Pacific. The deeper ocean continues to warm year after year.
For the seventh consecutive year, global annual mean sea level
became the highest in the 26-year record, rising to 81 mm
above the 1993 average. As anticipated in a warming climate,
the hydrological cycle over the ocean is accelerating: dry
regions are becoming drier and wet regions rainier.
Closer to the equator, 95 named tropical storms were
observed during 2018, well above the 1981–2010 average of
82. Eleven tropical cyclones reached Saffir–Simpson scale Category 5 intensity. North Atlantic Major Hurricane Michael’s
landfall intensity of 140 kt was the fourth strongest for any
continental U.S. hurricane landfall in the 168-year record. Michael caused more than 30 fatalities and $25 billion (U.S. dollars) in damages. In the western North Pacific, Super Typhoon
Mangkhut led to 160 fatalities and $6 billion (U.S. dollars) in
damages across the Philippines, Hong Kong, Macau, mainland
China, Guam, and the Northern Mariana Islands. Tropical
Storm Son-Tinh was responsible for 170 fatalities in Vietnam
and Laos. Nearly all the islands of Micronesia experienced at
least moderate impacts from various tropical cyclones.
Across land, many areas around the globe received copious
precipitation, notable at different time scales. Rodrigues and
Réunion Island near southern Africa each reported their third
wettest year on record. In Hawaii, 1262 mm precipitation at
Waipā Gardens (Kauai) on 14–15 April set a new U.S. record
for 24-h precipitation. In Brazil, the city of Belo Horizonte
received nearly 75 mm of rain in just 20 minutes, nearly half
its monthly average.
Globally, fire activity during 2018 was the lowest since the
start of the record in 1997, with a combined burned area of
about 500 million hectares. This reinforced the long-term
downward trend in fire emissions driven by changes in land
use in frequently burning savannas. However, wildfires burned
3.5 million hectares across the United States, well above the
2000–10 average of 2.7 million hectares. Combined, U.S. wildfire damages for the 2017 and 2018 wildfire seasons exceeded
$40 billion (U.S. dollars).
https://www.ametsoc.net/sotc2018/Socin2018_lowres.pdf
