(Sorry for cross postings)
Brazil takes centre stage
Nature Climate Change | Editorial
25 May 2012
Brazil's hosting of the much anticipated Rio+20 United Nations
Conference on Sustainable Development this month will put the country
in the climate change spotlight.
The Rio+20 conference (20ï¿½22 June 2012) will be held in Rio de
Janeiro, Brazil. It will focus on two main themes ï¿½ development of a
green economy while fostering sustainable development and poverty
eradication, and the institutional frameworks necessary to achieve
these goals, including the strengthening of international
environmental governance. Areas identified for 'priority attention'
are employment, energy, sustainable cities, food security, and
sustainable agriculture, water, oceans and disaster readiness.
Brazil -- the fourth biggest greenhouse-gas emitter in the world --
has so far made limited progress in limiting emissions, and, as
discussed by Eduardo Fernandez Silva (page 379), the measures so far
announced under the National Policy on Climate Change Law (enacted in
December 2009) are unlikely to achieve much more. The intention of the
law is to set in place measures to reduce emissions. The authorities
hope that by 2020, emissions will have fallen to around 2005 levels.
Many question whether this target will be achievable in the absence of
attractive economic incentives for environmentally responsible
behaviour along with strong sanctions against misbehaviours.
In essence, Brazil needs to move beyond good intentions and start to
implement practical measures. To be fair, the nation has started to
reduce deforestation in the Amazon and limit damaging land-use change
through sustainable management. However, as discussed by Silva, what
has so far been announced in relation to other sectors such as
industry look less promising.
Apart from obvious greenhouse-gas sources such as heavy industry,
considerable amounts of carbon dioxide and methane are released from
tropical dams. Much of the electricity consumed in Brazil comes from
hydroelectric power plants. And yet, as discussed by Philip Fearnside
and Salvador Pueyo (page 382), emissions from tropical dams rarely
feature prominently in national or global greenhouse-gas inventories.
Even when greenhouse-gas emissions from tropical dams are considered,
they are often underestimated or misreported. There is no excuse for
this ï¿½ reliable methods exist for measuring emissions from
reservoirs, as well as from turbine outlets and downstream river
flows, and for up-scaling estimates. It does not help when, as
documented by Fearnside and Pueyo, a major Brazilian electric
utilities company gets its sums wrong, thereby seriously
underestimating total reservoir surface emissions from Brazil's
largest dams. But even setting aside such sloppiness -- and indeed the
loss of river and forest habitat caused by dam construction --
tropical hydroelectric plants are not quite as green as often
portrayed, and certainly no panacea for dealing with the problem of
emissions from the energy sector.
This leads on to a more general point. It is often naively assumed
that energy from fossil fuels can be replaced in a one-to-one manner
with energy from renewable sources -- that is that one unit of
renewable energy displacing one unit of fossil-fuel energy. Indeed,
this is an implicit assumption of reports prepared by the
Intergovernmental Panel on Climate Change. However, as reported by
Richard York (page 441), the assumed relationship has not held for
most nations of the world over the past 50 years.
York finds that, on average, less than one-quarter of a unit of fossil-
fuel energy use is displaced by each unit of total national energy use
from non-fossil-fuel sources. Focusing solely on electricity, the
situation is considerably worse. As Andrew Jorgenson puts it in an
accompanying News & Views (page 398), "York's findings contradict the
widely held assumption that the expansion of alternative energy
production will proportionally suppress fossil-fuel energy
production." Jorgenson goes on to outline both the implications and
limitations of the study, but echoes the call of many that the best
way of reducing emissions is for all of us, individually and
collectively as societies, to consume less energy.
As already mentioned, one of the areas highlighted for attention by Rio
+20 is disaster readiness. On page 462, Ning Lin and colleagues
consider the likelihood of increased hurricane threat under climate
change, taking as a case example New York City, which is increasingly
vulnerable to flooding under storm-surge conditions. Using computer
simulations, the researchers show how the combined effects of changes
in storm climatology and sea-level rise could greatly increase the
frequency of surge flooding over the next century. Their findings
suggest that now is the time to initiate long-term adaption planning
so as to avert the worst impacts on property, infrastructure and the
safety of the city's citizens-- a theme expanded on by Jeroen Aerts
and Wouter Botzen on page 377.
Meanwhile, as discussed by Allan Findlay on page 401, a recently
published study (C. L. Gray and V. Mueller Proc. Natl Acad. Sci. USA
109, 6000-6005; 2012) has shown that climate change-related flooding
in a rather different context-- that of rural Bangladesh-- may be
relatively unimportant compared with non-climate-related crop failure
in driving human migration. So, could it be that warnings from
environmentalists that climate change will inevitably lead to forced
mass human migrations are mere scaremongering?
That is probably going too far, but as Findlay notes, even if
migration is a practical option, the decision to 'up sticks' and move
is likely to involve multiple, complex and intertwined factors. This
view is given further credence, by a study conducted by Dominic
Kniveton and colleagues in the landlocked west-African country Burkina
Faso (page 444). They find that owing to complex interactions between
climate, rainfall variability and various socio-economic factors,
migration could increase or decrease over the next few decades,
depending on the scenario considered ï¿½ issues further discussed in
an accompanying News & Views by Etienne Piguet (page 400).
Moving to agriculture, there is now a not-so-small industry of
researchers looking to predict the possible impacts of climate change
on regional, national and global scales. Much of this work is intended
to inform policy. However, a dispute about projected future wheat
yield trends in the United Kingdom (pages 378 and 380) highlights, at
the very least, the critical importance of clarity in communicating
climate change evidence. We trust that whatever comes out of Rio+20
will be reported in a clear and unambiguous manner, reducing the
potential for unnecessary misunderstanding and rancour.
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