Hockey sticks to huge methane burps: Five papers that shaped climate science in 2013
- 27 Dec 2013, 11:00
- Roz Pidcock
There's no doubt, 2013 was a busy year in climate science. As
well as a bumper new climate report from the UN's official climate
assessment body - the Intergovernmental Panel on Climate Change (IPCC) - a few bits of research
caused quite a stir on their own.
We've cast our collective Carbon Brief mind back over the year
to find the five science papers that had everybody talking.
What hockey stick graphs tell us about recent climate
Using fossils, corals, ice cores and tree rings, a study
in the journal Science in March became the first to take a
11,300-year peek back into earth's temperature history.
Shaun Marcott and colleagues
showed global temperature rose faster in the past century than
it has since the end of the last ice age, more than 11,000 years
The story piqued the interest of
The Daily Mail and
The Evening Standard. And as an extension of Michael Mann's
stick" graph, the paper attracted a good deal of attention from
climate skeptic corners
Global temperature reconstructed for the past 11,300 years
by Marcott et al. (purple line) and for the past 2,000 years by
Mann et al. (grey lines) Source:
Marcott, S. A. et al., (2013) A Reconstruction of Regional
and Global Temperature for the Past 11,300 Years. Science, DOI:10.1126/science.1228026
oceans are getting warmer, faster
study led by UK researcher Magdalena Balmaseda highlighted why
its important not to overlook the oceans when thinking about
Publishing in the journal Geophysical Research Letters, the
just how much the oceans have warmed in the past 50 years - and
that the pace accelerated sharply after about 2000.
The data suggests heat is finding its way to the deep ocean,
rather than staying in the upper layer. That could be
one reason for less surface warming in the last 15 years than
in previous decades, suggested the authors. Lead author Kevin
Trenberth told Carbon Brief:
"[The new study] means that the current
hiatus in surface warming is transient and global warming has not
Amount of heat stored in the whole ocean in past five
decades (purple), the top 700 m (blue) and just the top 300 m
(grey). Source: Balmaseda et al., (
The paper just missed the deadline for consideration in the
recent IPCC report. But as a potential
explanation for the so-called surface warming
oceans still got a fair bit of media attention when the report
finally came out in September.
Balmaseda, M. A., Trenberth, K. E. & Källén, E. (2013)
Distinctive climate signals in reanalysis of global ocean heat
content. Geophysical Research Letters,
Surface warming slowdown doesn't affect climate sensitivity, study
This was the year climate sensitivity became a thing. The degree
of earth's sensitivity to greenhouse gases is key to understanding
climate change. This year, a particularly technical way to measure
it made the leap from the quiet corridors of scientific institutes
to the mainstream media.
brought the issue to the masses in April by suggesting slower
than expected warming in recent years meant scientists were
rethinking how sensitive the climate is.
But it was a
case of mistranslation by the Economist and a paper by
Alexander Otto a month later put paid to the idea. Climate
sensitivity is pretty nuanced stuff, but the paper's gist was that
recent sluggish surface temperatures have no bearing on the warming
we can expect in the long term.
The authors' climate sensitivity estimate sat just below the
likely range put forward by the IPCC. While not a conclusive
argument for shifting the range altogether, Otto told us it might
support lowering the bottom boundary a bit - and this is what
happened when the IPCC released its
The authors' prediction for the next few decades caused a bit of
a stir too. The prospect of less warming than previously thought -
because heat is temporarily entering the oceans - prompted some
jump to the conclusion that climate change no longer poses a
Otto, A. et al., (2013) Energy budget constraints on climate
response. Nature Geoscience, DOI:10.1038/ngeo1836
How likely is a huge Arctic methane pulse? We find disagreement
Rising temperatures in the Arctic could see 50 billion tonnes of
methane currently frozen in the seabed released into the atmosphere
over ten years, a Nature
comment piece argued in July.
The paper's topline figure
pricked the media's ears - that the climate change consequences
of that amount of methane could cost a whopping $60 trillion.
Expressing the result of huge and sudden methane release as an
economic cost is a new concept. But the study's novelty was
eclipsed by scientists'
criticisms that a 50 billion tonne pulse was "totally
unjustified". Professor David Archer from the University of Chicago
told Carbon Brief:
"No one has proposed any mechanism for
releasing methane that wouldn't take centuries, not just a few
Dr Nafeez Ahmed, whose blog for the Guardian reported the
conceded the perils of attaching too much weight to one study,
saying he hadn't realised the scenario was "speculative".
Whiteman, G., Hope, C. & Wadhams, P. (2013) Climate
science: Vast costs of Arctic change. Nature Climate Change,
The so-called surface warming slowdown - and what may be driving
it - has been quite a
media preoccupation in the past year -
particularly in the run up to the IPCC report launch in
Research earlier in the year suggested
natural cycles could be squirrelling heat away into the deep ocean.
Cuts in CFCs under the Montreal Protocol could be contributing too,
But a paper published in November
shed new light on this much-discussed topic, suggesting
temperature rise in the last decade and a half may be nothing
unusual after all.
The authors said plugging well-known gaps in one of the major
global datasets - particularly in the Arctic - brings the rate of
warming since 1997 much more in line with previous decades.
Warming after 1997 in the original temperature data (thin
red line) compared to the updated data (thick red line). Source:
Cowtan & Way (2013)
Coming on the heels of a year of heated speculation, the paper
met with plenty of
interest from climate scientists and skeptics alike.
So where does it leave the slowdown? This
RealClimate blog does a good job of explaining how different
explanations for slower warming fit together. The gist is there is
still evidence for a slowdown, but the magnitude may not be as
great as previously thought.
won't be the last word on the slowdown, warn the authors. Lead
author Kevin Cowtan had another salient point to make, looking at
short time periods "has dominated the public discourse but is in
our view a misleading approach to evaluating climate science."
Cowtan, K. & Way, R.G. (2013) Coverage bias in the
HadCRUT4 temperature series and its impact on recent temperature
trends. Quarterly Journal of the Royal Meteorological Society, DOI: