Friday 21 November 2008, San José, Costa
Rica
CLIMATE CHANGE:
Hot Days and Nights in
Mexico 2090
By Stephen Leahy*
UXBRIDGE, Canada (Tierramérica)
- Climate change will
dramatically increase
the number of hot, dry
days in Mexico in the
coming decades, while
coastal regions like the
Yucatán, in the
southeast, will be
swamped by sea levels
that are half a metre
higher than today, a new
study has found.
By 2030, Mexico's
average daily
temperature is likely to
climb 1.4 degrees
Celsius above what has
been the average for the
past 30 years. By 2090,
this increase could
rocket upwards by 4.1
degrees, virtually
guaranteeing hot days
and nights for 80 to 90
percent of the year,
says the Oxford
University study
financed by the United
Nations Development
Programme (UNDP).
Cold weather will become
very rare in Mexico
according to data from
the Intergovernmental
Panel on Climate Change
(IPCC), an umbrella
organisation of
scientists from around
the world and the
preeminent authority on
climate change.
"Mexico is one area of
the world where all the
computer climate models
agree," says Carol
McSweeney of the School
of Geography and
Environment at Oxford.
Computer climate models
incorporate the physics
of the atmosphere and,
often, the ocean, sea
ice and land surface as
well, to project what
the future climate may
be as carbon emissions
from the burning of
fossil fuels continue to
rise, trapping more heat
in the atmosphere.
The IPCC, co-winner of
the 2007 Nobel Peace
Prize, used the data
from two dozen different
climate models powered
by the world's fastest
supercomputers to issue
its landmark Fourth
Assessment Report last
year.
That report warned the
world that carbon
emissions from the
burning of fossil fuels
are causing the current
rise in global
temperatures that could
hike the global average
temperature 4.5 degrees
C by 2100.
But McSweeney and her
Oxford colleagues
wondered: what does that
mean for individual
countries? With UNDP
funding, they have used
the IPCC climate model
data to determine the
potential changes in the
climate of 52 developing
nations.
The study, presented
Nov. 5, includes five
Latin American
countries: Cuba,
Dominican Republic,
Mexico and Nicaragua.
"We thought it was
important to boil down
all that complex data
and create a summary
report of what the data
shows," McSweeney told
Tierramérica.
In rare universal
agreement, the highly
complex models show
Mexico will get much
hotter and drier and
that this will happen
soonest in the north and
central regions of the
country, says McSweeney.
Climate change has
already made the country
warmer by about 0.6 C
since 1960, according to
the study. The number of
hot days increased by 36
per year between 1960
and 2003.
Hot days are defined as
the warmest 10 percent
of the days over a
30-year span and are
"what people normally
would consider to be
quite hot," McSweeney
explained.
By 2060, one-third of
all days will be "hot"
by current standards,
and by 2090 more than
half the year will be
like the hottest days of
the year presently. On a
regional basis, central
and northern Mexico
(including Mexico City)
are projected to
experience temperatures
that are six and seven
degrees higher than the
current norm.
Cold days will be
exceedingly rare by 2090
-- perhaps just three or
four days a year.
The main purpose of the
study is to fill in the
gaps of information of
climate change in
developing countries.
In Mexico, "it hasn't
been easy" to provide
climate information, and
"we still can't
completely rely on it,"
Juan González,
coordinator of the
doctoral programme in
environmental law at the
Autonomous Metropolitan
University, told
Tierramérica.
"The federal government
and the states make
measurements using
different methodologies,
and in many cases they
aren't compatible,"
González added.
The Oxford study shows
that the mean rainfall
over the entire country
has not changed since
1960, although there are
wide regional
variations. The number
of intense or heavy
rainfall events has
increased by about 1.2
percent per decade.
But all models show a
reduction in annual
rainfall between three
and 15 percent by 2090.
Regional variations are
difficult to predict
because the models
cannot simulate tropical
cyclones, hurricanes or
the cyclical El Niño/La
Niña climate events,
McSweeney pointed out.
"These projections must
be used with caution and
awareness of their
shortcomings," she said.
Future regional rainfall
estimates are one of
those shortcomings, says
Gavin Schmidt, a climate
modeler at the NASA
Goddard Institute for
Space Studies in New
York.
But Schmidt told
Tierramérica that the
UNDP/Oxford report "is a
useful summary in terms
of letting people in
these countries know
what is coming."
One other caveat is that
these reports do not
reflect sea level rise
from climate change. The
IPCC acknowledges that
its data did not include
the melting of the
world's glaciers and ice
sheets in the Arctic and
Antarctic, says Schmidt,
who is a member of the
IPCC.
The ice melt is adding
measurably to the sea
level rise from thermal
expansion of the oceans,
he said. That is likely
to mean greater impacts
from ocean erosion and
storm surges on flat,
low-lying areas such as
the Yucatán Peninsula,
where the sea could rise
as much as 56
centimetres.
The data also shows that
in tropical and
sub-tropical countries,
warm season temperatures
will be hotter than
anything ever
experienced previously
starting as soon as
2050.
"It's important to
understand that these
will be unprecedented
conditions," said
Schmidt.
McSweeney hopes
scientists and policy
makers in Mexico review
the report and send in
their feedback or use
the freely available
IPCC climate model data
to do their own
analyses.
"We hope this is useful
information, but further
study is needed before
making any policy
decisions," she said.
The problem, said
González, is that
"Mexico still has
short-term plans in
which climate change is
mentioned as a
reference. There is no
ambitious, realistic
plan for developing
alternative energy and
changing course."
In fact, "a reform was
just approved for the
petroleum industry that
reiterates the focus on
development based on
that finite,
greenhouse-gas-generating
sector," said González.
Oil is Mexico's main
source of revenues.
*With reporting by Diego
Cevallos from Mexico
City.
(*This story was
originally published by
Latin American
newspapers that are part
of the Tierramérica
network. Tierramérica is
a specialised news
service produced by IPS
with the backing of the
United Nations
Development Programme,
United Nations
Environment Programme
and the World Bank.) |
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