The effect of the Kyoto Protocol on global warming
On the Record
Mar 22, 2010 - by Staff
Tom M.L. Wigley
Spring 2006
Now retired, Tom Wigley was an NCAR Senior Scientist when this statement was published in 2006.
Kyoto Protocol implications for carbon dioxide, temperature, and sea level
Summary
Tom
Wigley in 1998 reported research showing that adherence to the Kyoto
Protocol alone, without subsequent action, would have a minimal impact
on global warming.
In the article, published in Geophysical Research Letters (see below),
he concluded: "This does not mean that the actions implied by the Protocol are
unnecessary." He called the protocol an important first step while
pointing out that much more must be done after Kyoto to reduce future
global warming by a significant amount.
Wigley used
computer modeling to test several emissions scenarios for the "Annex B"
countries—the industrialized and nearly industrialized countries called
upon to reduce greenhouse gas emissions in the protocol. Each scenario
was played out through 2010 (the midpoint of the Kyoto commitment
period of 2008–2012) and then extended to the end of the century.
The
first scenario looked at what would happen if, after the protocol
expires, the Annex B countries continued to abide by Kyoto's limits but
did not make any new commitments to further cut emissions for the rest
of the century.
This "constant compliance" scenario
would shave 0.11 to 0.21 degrees Celsius (0.20–0.38 degrees Fahrenheit)
off global average temperatures by 2100. Stated another way, instead of
heating up by 2.5°C (4.5°F), a midpoint in the range of projections of
global warming, Earth would warm approximately 6% less.
For comparison, the study also examined a "business as usual" or "no climate policy" case. The starting point was IS92a, an emissions scenario included in the 2001 report of the Intergovernmental Panel on Climate Change,
that incorporates a slight tapering off in emissions later this century
due to global economic and social activities unrelated to climate
change.
Wigley concluded that the impact on projected
temperature increases, with all countries doing only what is required
under Kyoto and then continuing with business as usual, would be a
scant 0.06 to 0.11°C (0.11 to 0.20°F) shaved off the total warming,
roughly a 3% reduction.
He also considered a third
scenario in which the Annex B countries continue to reduce their
emissions after the Kyoto period by 1% per year (a scenario that, like
the other two scenarios, assumes continued growth of emissions in
developing countries at a business-as-usual rate). In this case, the
warming reduction by 2100 would be some 14%.
In a 2005 article in Science (see below),
Wigley found that Earth is already warming due to human actions.
Averting further warming will require a global reduction in
human-generated greenhouse gases by all nations, developed and
developing, to substantially below present levels.
Articles
Geophysical Research Letters: The Kyoto Protocol
Wigley, T.M.L. (1998), "The Kyoto Protocol: CO2, CH4 and climate implications," Geophysical Research Letters, vol. 25, pp. 2285–88.
Abstract
Kyoto Protocol implications for CO2,
temperature and sea level are examined. Three scenarios for post-Kyoto
emissions reductions are considered. In all cases, the long-term
consequences are small. The limitations specified under the Protocol
are interpreted in terms of both CO2 and CH4
emissions reductions and a new emissions comparison index, the Forcing
Equivalence Index (FEI), is introduced. The use of GWPs [Global Warming
Potential values] to assess CO2-equivalence is assessed.
Excerpts from the conclusion
Three Kyoto Protocol cases have been examined. These extend the Protocol beyond [2010]1 by assuming no further reductions in Annex B emissions;2 constant Annex B emissions; or a decline in Annex B emissions at 1% compound per year.3
. . .
Large additional emissions reductions are required at some future date
(certainly earlier than 2040) if concentration stabilization is to be
achieved at 550 ppmv [parts per million by volume] or lower.
. . .Finally, reductions in temperature and sea level rise under the
Protocol and the extensions considered here are relatively small, but
nonetheless important as a first step towards stabilizing the climate system. (emphasis added)___
Notes
1The paper lists the date as 2100, a typographical error corrected here to 2010.
2This is the "business as usual" case.
3These latter two cases correspond to the imposition of
either small or modest emissions-reduction policies, but only in Annex
B countries, not globally.
Science: The Climate Change Commitment
Wigley, T.M.L. (2005), "The Climate Change Commitment," Science, vol. 307, pp. 1766–69.
Abstract
Even
if atmospheric composition were fixed today, global-mean temperature
and sea level rise would continue due to oceanic thermal inertia. These
constant-composition (CC) commitments and their uncertainties are
quantified. Constant-emissions (CE) commitments are also considered.
The CC warming commitment could exceed 1°C. The CE warming commitment
is 2° to 6°C by the year 2400. For sea level rise, the CC commitment is
10 centimeters per century (extreme range approximately 1 to 30
centimeters per century) and the CE commitment is 25 centimeters per
century (7 to 50 centimeters per century). Avoiding these changes
requires, eventually, a reduction in emissions to substantially below
present levels. For sea level rise, a substantial long-term commitment
may be impossible to avoid.
Excerpt from the conclusion
The CE results reinforce the common knowledge that, in
order to stabilize global-mean temperatures, we eventually need to
reduce emissions of greenhouse gases to well below present levels.4
The CC results are potentially more alarming, because they are based on
a future scenario that is clearly impossible to achieve and so
represent an extreme lower bound to climate change over the next few
centuries. For temperature, they show that the inertia of the climate
system alone will guarantee continued warming and that this warming may
eventually exceed 1°C. For sea level, a continued rise of about 10
cm/century for many centuries is the best estimate. Although such a
slow rate may allow many coastal communities to adapt, profound
long-term impacts on low-lying island communities and on vulnerable
ecosystems (such as coral reefs) seem inevitable. (emphasis added)___
Notes
4See T.M.L. Wigley, R. Richels, J.A. Edmonds (1996), "Economic and environmental choices in the stabilization of atmospheric CO2 concentrations," Nature, vol. 379, pp. 240–243.
Related Links
For background
UN Framework Convention on Climate Change (three languages available)
Relationship of Kyoto Protocol to UN Framework Convention
Text of the Kyoto Protocol (six languages available)
UN Environment Programme: Climate Change
For research
MAGICC and SCENGEN Computer Models
These coupled, interactive software suites were used in the 2001 IPCC Third Assessment Report
and by Wigley for the 1998 article. The software allows experimenters
to investigate future climate change and its uncertainties at both the
global-mean and regional levels.