CO2 emission reduction assumptions overly optimistic, says study

Reducing global emissions of carbon dioxide this century is going to be more challenging than society has been led to believe, according to a new research commentary article appearing April 3 in Nature.

The authors, from the University of Colorado at Boulder, the National Center for Atmospheric Research in Boulder and McGill University in Montreal, said the technological challenges of reducing CO₂ emissions have been significantly underestimated by the Intergovernmental Panel on Climate Change. The study concludes the IPCC is overly optimistic in assuming that, even without action by policymakers, new technologies will result in dramatic reductions in the growth of future emissions.

Recent changes in “carbon intensity” -- CO₂ emissions per unit of energy consumption -- already are higher than those predicted by the IPCC because of rapid economic development, said lead author and CU-Boulder Professor Roger Pielke Jr. of the environmental studies program. In Asia, for instance, the demands of more energy-intensive economies are being met with conventional fossil-fuel technologies, a process expected to continue there for decades and eventually move into Africa.

The IPCC underestimate of carbon intensity is due in part to the panel’s differing scenarios tied to global emission changes expected to occur spontaneously and those driven by climate policies, according to the Nature authors. Titled “Dangerous Assumptions,” the Nature commentary was co-authored by Senior Scientist Tom Wigley of NCAR’s Climate and Global Dynamics Division and economics Professor Christopher Green of McGill University’s Global Environmental and Climate Change Center.

“According to the IPCC report, the majority of the emission reductions required to stabilize CO₂ concentrations are assumed to occur automatically,” said Pielke. “Not only is this reduction unlikely to happen under current policies, we are moving in the opposite direction right now. We believe these kind of assumptions in the analysis blind us to reality and could potentially distort our ability to develop effective policies.”

Stabilization of atmospheric concentrations of CO₂ and other greenhouse gases was the primary objective of the 1992 United Nations Framework Convention on Climate Change approved by almost all countries, including the United States, said Wigley.

“Stabilization is a more daunting challenge than many realize and requires a radical ‘decarbonization’ of energy systems,” said Wigley. “Global energy demand is projected to grow rapidly, and these huge new demands must be met by largely carbon-neutral energy sources -- sources that either do not use fossil fuels or which capture and store any emitted CO₂.”

Calculations by the Nature authors show that at least two-thirds of the amount of carbon that has to be removed from the energy supply in order to stabilize atmospheric CO₂ concentrations at roughly 500 parts per million is assumed to occur automatically by the IPCC authors. Atmospheric CO₂ levels are currently at about 390 parts per million.

Enormous advances in energy policy in the coming decades will be needed to stabilize atmospheric concentrations of CO₂ at levels currently considered “acceptable,” the Nature authors concluded.

Unlike the IPCC authors, who built in assumptions about future “spontaneous” technological innovations, the Nature commentary authors began with a set of “frozen technology” scenarios as baselines -- scenarios in which energy technologies are assumed to stay at present levels. “With a frozen technology approach, the full scope of the carbon-neutral technology challenge is placed into clear view,” said Green.

“In the end, there is no question whether technological innovation is necessary -- it is,” the authors wrote in Nature. “The question is, to what degree should policy focus explicitly on motivating such innovation? The IPCC plays a risky game in assuming that spontaneous advances in technological innovation will carry most of the burden of achieving future emissions reductions, rather than focusing on those conditions that are necessary and sufficient for those innovations to occur.”

Source: University of Colorado at Boulder

Related stories:

CO2 increase in the atmosphere augments tolerance of barley to salinity
In future, climate change will bring an increase in salty surfaces on the Earth and in the concentration of CO₂ in the atmosphere. However, this higher CO₂ has some positive effects on the physiology of barley plants and increases its tolerance to salinity. This is the conclusion of the PhD thesis of Ms Usue Pérez-López, defended at the University of the Basque Country (UPV/EHU).
Canada's shores saved animals from devastating climate change 252 million years ago
The shorelines of ancient Alberta, British Columbia and the Canadian Arctic were an important refuge for some of the world's earliest animals, most of which were wiped out by a mysterious global extinction event some 252 million years ago.
CO2 emissions booming, shifting east, researchers report
Despite widespread concern about climate change, annual carbon dioxide emissions from burning fossil fuels and manufacturing cement have grown 38 percent since 1992, from 6.1 billion tons of carbon to 8.5 billion tons in 2007.
Warming world in range of dangerous consequences
The earth will warm about 2.4° C (4.3° F) above pre-industrial levels even under extremely conservative greenhouse-gas emission scenarios and under the assumption that efforts to clean up particulate pollution continue to be successful, according to a new analysis by a pair of researchers at Scripps Institution of Oceanography at UC San Diego.
Science paper examines role of aerosols in climate change
A group of scientists affiliated with the International Geosphere-Biosphere Programme (IGBP) have proposed a new framework to account more accurately for the effects of aerosols on precipitation in climate models. Their work appears in the 5 September issue of Science magazine.
Ice Age lesson predicts a faster rise in sea level
If the lessons being learned by scientists about the demise of the last great North American ice sheet are correct, estimates of global sea level rise from a melting Greenland ice sheet may be seriously underestimated.
Protecting natural forests crucial for climate change
(PhysOrg.com) -- South-east Australia’s natural forests are among the most carbon dense in the world and store three times more carbon than Australian and international climate change experts realise, a world-first study released today at The Australian National University revealed.
Acidifying oceans add urgency to CO2 cuts
It's not just about climate change anymore. Besides loading the atmosphere with heat-trapping greenhouse gases, human emissions of carbon dioxide have also begun to alter the chemistry of the ocean—often called the cradle of life on Earth. The ecological and economic consequences are difficult to predict but possibly calamitous, warn a team of chemical oceanographers in the July 4 issue of Science, and halting the changes already underway will likely require even steeper cuts in carbon emissions than those currently proposed to curb climate change.

News discussion:

Space & Earth science news