2019 was a warm year,
but cooler than 2016.
2016 had been warmed
by an El Nino heat release
from the Pacific Ocean.
Since satellite global
average temperature
measurements began
in 1979, the lower
troposphere ( where
the greenhouse effect
occurs ) temperatures
have increased over
both land and oceans.
Warming over land
is much more than
warming over oceans.
This could be caused
by variations in
cloud cover and/or
changes in land use.
"Global" warming
after 1980 has
mainly been
a Northern
Hemisphere
trend, with much
of the warming
from 1994 to 1999.
Antarctica
temperatures
remained almost
stable since the
satellite record
began in 1979.
A stratosphere
(above troposphere)
temperature ‘pause’
has existed for about
5 years.
Ocean Temperatures
at Different Depths:
The Argo program
has had 15 years
of global coverage,
growing from
1,000 floats in 2004
to more than 4,000
floats in early 2020.
Since 2004, when
detailed recording of
ocean temperatures
began, the global
oceans above a
1900 meter depth
have warmed slightly,
on average.
Sea level
is monitored by
satellite altimetry,
and also direct
measurements
using tide gauges
along coasts.
Tide gauges suggest
an average global
sea-level rise
of 1.0 to 1.5 mm/year,
while satellite data
suggest a rise of
about 3.2 mm/year,
or more.
The difference has
no good explanation.
Neither of the two types
of measurements indicate
any modern acceleration
in sea level rise.
Since 1979, Arctic and
Antarctic sea-ice extents
have had opposite trends,
decreasing and increasing,
respectively.
Northern Hemisphere
snow cover extent
has been stable
since 1972.
Tropical storms
and hurricanes have had
large annual variations
in accumulated
cyclone energy (ACE)
since 1970, but there
has been no overall trend.
Also, no trend in U.S.
for hurricane landfalls,
since records began
in 1851.
The annual change
in tropospheric CO2
has been increasing,
from about +1 part
per million (ppm)
per year in the
early part of the
record since1958
to more than
2.5 ppm/year,
towards the end
of the record