Sad to say this is only my second post of September. I have been busy with other things... extensive travel.... re-roofing a barn... the usual. Anyway, just a couple of links I'd like to mention in connection to my
most recent Bloomberg column, which appeared yesterday.
The point of my column was to emphasize just how complex the science of the Earth's climate really is. I was struck by two recent articles in Nature, both of which are worth reading. One,
an excellent feature by Nicola Jones, describes a few of the counter-intuitive effects of climate, for example, how the sea can rise (or fall) in different ways in different places. Water doesn't just spread out, as you might intuitively think. It has mass, and inertia, gets blown by winds, etc., and can pile up. A short taste:
When Jeff Freymueller, a geophysicist at the University of Alaska
Fairbanks, visited Alaska's Graves Harbor more than a decade ago, his
marine charts showed three isolated little islands; what he saw,
instead, were three grassy peninsulas connected to the mainland. That
was because water levels in some parts of Alaska are dropping — by up to
3 centimetres per year.
The ground there is
lifting upwards, in a slow-motion rebound that has been going on for
10,000 years, since the glacial ice sheet that once weighed down the
continent receded at the end of the last ice age. Gravitational
influences on the oceans are also at work: as local glaciers recede and
the Greenland ice sheet melts, their gravitational pull is subtly
reduced, allowing more ocean water to slop southwards.
Trends
in local sea level can differ strongly from the global average, which
is increasing by around 3.2 millimetres per year. “Some places,
sea-level rise is ten times faster than the average,” says Jerry
Mitrovica, a geophysicist at Harvard University in Cambridge,
Massachusetts.
One side of this equation is
the movement of the land. Canada's Hudson Bay, for example, was once
buried under more than 3 kilometres of ice, and the release from that
load is now causing the land to rise at about 1 centimetre per year. As
that part of North America moves upwards, land to the south is being
levered down: the US east coast is dropping by millimetres per year.
Subsidence
can cause some areas to sink much faster. Compaction of river sediments
and hollowing out of the earth by groundwater extraction, for example,
are causing parts of China's Yellow River delta to sink at up to 25
centimetres per year4.
Adding
to the complexity, the oceans do not rise evenly all over the world as
water is poured in. Air pressure, winds and currents can shove water in a
given ocean to one side: since 1950, for example, a 1,000-kilometre
stretch of the US Atlantic coast north of Cape Hatteras in North
Carolina has seen the sea rise at 3–4 times the global average rate5.
In large part, this is because the Gulf Stream and the North Atlantic
current, which normally push waters away from that coast, have been
weakening, allowing water to slop back onto US shores.
Finally,
waters near big chunks of land and ice are literally pulled up onto
shores by gravity. As ice sheets melt, the gravitational field weakens
and alters the sea level. If Greenland melted enough to raise global
seas by an average of 1 metre, for example, the gravitational effect
would lower water levels near Greenland by 2.5 metres and raise them by
as much as 1.3 metres far away.
Scientists and engineers are only just
starting to wrangle all these effects into local projections. In June,
the New York City Panel on Climate Change updated its estimates of
sea-level rise by including the local effects of gravitational shifts6.
Panel members concluded that they expect to see 30–60 centimetres of
rise by 2050. Finding and combining the right data sets took about six
months; the exercise should pave the way for other cities to do the
same, says Cynthia Rosenzweig, a climate-impact researcher at NASA's
Goddard Institute for Space Studies in New York City. “We really are
working to get the best science.”
Equally interesting and informative, in a very different way, is
a commentary piece in the same issue by K. John Holmes. This looks at the history of the use and management of the arid lands in the central and western US. Sounds a little boring, but Holmes argues that the process then was just as messy, just as fraught with hysteria and massive disinformation, as is the current debate over climate change and what to do about it:
When nineteenth-century explorer William Gilpin travelled across the
Great Plains, the expanse that covers much of the central and western
United States, he marvelled at the “great pastoral region”, the dry
climate of which was “favorable to health, longevity, intellectual and
physical development”1.
Great cities could be built there, he imagined, taking advantage of the
wealth of local resources — rivers, forests and even gold.
Geologist
John Wesley Powell saw things differently. Moving from the humid east
to the arid west would affect agricultural practices, occupations,
social interactions and political customs, he contended2, 3.
Dry-land agriculture could not support a large population; any towns
built in the west would need appropriate designs, irrigation and
resource management. A controversy erupted.
The ensuing debates about how the
arid lands should be settled hold lessons for us today on adapting to a
changing climate. At their heart was a development plan for the region
that Powell published in 1878 (ref. 2).
It called for detailed scientific and engineering surveys, and analysis
to inform land-use plans and laws. Although it addressed a spatial
change in conditions caused by westward population expansion, Powell's
coupling of physical and human dimensions was a forerunner to the
assessment approach used today by the Intergovernmental Panel on Climate
Change (IPCC).
Powell's plan was never
implemented in its entirety, but it began an era in which large-scale
environmental and natural-resources assessments became central to the
policy process in the United States4.
Stalled by misinformation, political controversy and recessions,
legislation for allocating resources in the arid lands took decades to
enact. Then, as now, the assessments and their validity became part of
the debate. Eventually, extreme weather, including long droughts, pushed
policy-makers to act.
Read the whole thing
here.