NASA scientists: Expect record-breaking warm years soon
- 27 Jan 2012, 16:07
- Verity Payne
We're barely out of 2011, and already there's plenty of
discussion about last year's temperatures and how they fit with the
global warming trend.
Over the past few weeks, the major temperature datasets have
been giving their assessment of how temperatures behaved last year.
First up: the UK's Met Office, who released preliminary data
putting 2011 as the UK's
second warmest year on record - (remember that any one year
doesn't tell us much about the long term trend, as we pointed
out at the time, although lots of hot years together do).
Then the global temperature records starting coming, with the US
National Oceanographic and Atmospheric Administration (NOAA)
releasing their global stats for 2011. Their global temperature
dataset put 2011 as the
joint eleventh warmest year since records began in 1880. They
also highlighted that 2011
"...Marks the 35th consecutive year,
since 1976, that the yearly global temperature was above
average...Including 2011, all eleven years of the 21st century so
far (2001-2011) rank among the 13 warmest in the 132-year period of
record. Only one year during the 20th century, 1998, was warmer
than 2011."
Now it is the turn of the other major US global temperature
dataset, from NASA's Goddard Institute for Space Studies (GISS).
They put 2011 as the ninth
warmest year on record, and also highlighted that
"The first 11 years of the 21st century
experienced notably higher temperatures compared to the middle and
late 20th century... The only year from the 20th century in the top
10 warmest years on record is 1998."
The graphs below show the GISS record for global surface air
temperature anomaly since records began:
Global surface air temperature anomalies relative to
1951-1980 base period for (a) the 12-month running mean, and (b)
the 60-month and 132-month running means. Source: NASA
GISS.
The UK's Met Office and Hadley Centre released provisional
figures for their HadCRUT3 dataset in November last year also
putting 2011 as the
eleventh warmest year on record, but have yet to release the
definitive data.
The differences in how the three main datasets are constructed
are explored in more detail in this
blog, and in our global
temperature datasets profile.
NASA expects record warm year in two to three
years
We all know by now that natural variations in climate affect
global temperatures over short timescales, which is why we have to
look at longer-term trends in global temperature to get an idea of
the impact man-made greenhouse gas emissions are having on global
temperatures.
James Hansen and his colleagues at NASA have taken an look at 2011's global
temperatures, taking into account important natural climate
fluctuations, and speculate about what global temperatures might do
over the next few years.
We should point out, this is not peer-reviewed research - it's
more of a commentary - but it makes for interesting reading if
you're considering the question of whether global warming has
'stopped' or not.
The NASA scientists consider the main natural climate
fluctuations, including changing climate patterns like El Niño
Southern Oscillation (ENSO) and the solar activity cycle. (Volcanic
activity can also affect temperatures, but there have been no
eruptions on the scale required to impact global climate this
year.)
ENSO
The El Niño Southern Oscillation (ENSO) has two phases - El Niño
which involves the spreading of seawater which is warmer than
normal across the equatorial Pacific and La Niña, which is the
spreading of cooler than normal water over the same region. As the
graph below shows, short-term global temperature fluctuations
follow the ENSO cycle.
Global monthly and 12-month running mean surface
temperature anomalies relative to 1951-1980 base period, and
12-month running mean of the Niño 3.4 index.
Source: NASA
GISS.
2011 was dominated by a reasonably strong 'double-dip' La Niña.
The NASA scientists suggest that this cooled the climate, although
not as much as might be expected - probably due to the overall
warming influence of man-made greenhouse gases. Hansen argues that
under the return of El Niño conditions we could expect a warmer
global average temperature, saying:
"It's always dangerous to make predictions about El Niño, but
it's safe to say we'll see one in the next three years. It won't
take a very strong El Niño to push temperatures above 2010."
The Sun
Another important factor is solar activity. As the graph below
shows, the last few years have seen low solar activity, which has
had a small cooling effect on the climate. As solar activity rises
again, this won't be the case.
Solar irradiance from composite satellite-based time
series. Data sources: For 1976/01/05 to 2011/02/02
Physikalisch Meteorologisches Observatorium Davos, World Radiation
Center and for 2011/02/03 to 2012/01/11
University of Colorado Solar Radiation & Climate
Experiment. Data are concatenated using the 2010/02/03 to
2011/02/02 period.Source: NASA
GISS.
The NASA scientists point out that there tends to be a delay of
roughly eighteen months between solar cycle changes and its effect
on global temperature, so they anticipate that the sun will
probably remain a cooling effect in the near future, but this will
change to a warming effect over the next 3 - 5 years.
The prospect of enhanced solar activity and an El Niño event
over the next few years have led the NASA scientists to suggest
that
"...The slowdown of warming is likely to
prove illusory, with more rapid warming appearing over the next few
years"
Hansen says he expects a record-breaking global average
temperature in the next two to three years. We'll wait and see.