The temperature increase depends, in almost a straight-line fashion, on the accumulated burden of added carbon dioxide (CO2) and other greenhouse gases (GHGs) in the atmosphere: the more GHGs, the higher the global average temperature becomes. In other words, the world has made insufficient progress in recent years in reducing the use of coal, petroleum and natural gas (fossil fuels, which produce CO2 when burned), so that the atmospheric burden of GHGs continues to increase without meaningful restraint.
The Earth has already warmed by about 1.0°C (1.8°F) above preindustrial levels, causing many harms around the world. Even without further GHG emissions, the man-made GHG already added will remain in the atmosphere for thousands of years, causing continued long-term climate effects.
Comparing A Stringent Emission Goal to an Earlier, More Relaxed Goal. To avoid worse consequences, the countries of the world have to work toward limiting the total increase to 1.5°C (2.7°F) by 2050, which is lower and sooner than the 2.0°C (3.6°
F) originally set as the goal for 2100 in the Paris Agreement. Some comparisons of differences in projected changes between the two global average temperature increases, given in the report, are summarized here:
·
Global sea level increases by 2100 would
be 10 cm (4 in) less at 1.5°C
than at 2.0°C
warming. This is significant because
shorelines are most vulnerable not just to increased sea levels in calm
weather, but to flooding from higher and stronger storm surges in extreme
weather. Regardless, sea levels will continue
rising beyond 2100;
·
Global coral reefs would be destroyed because
of warmer water temperatures and a more acidic ocean composition, to the extent
of 70-90% at 1.5°C,
but essentially completely lost at 2.0°C. This is
important because reefs are complete ecosystems that support marine life, ultimately
providing much of the seafood that humans consume;
·
Climate-associated effects to human
livelihoods and health, food availability, water supplies, and economic growth
will be less at 1.5°C
than at 2.0°C;
and
·
Extremes of climate and weather on land
that we are already experiencing around the world (such as more intense
rainfall, worse flooding, more intense heat and drought, and worse forest
wildfires) would be worse at 2.0°C than at 1.5°C.
Rapid reductions in annual rates of GHG emissions
must be undertaken immediately to keep the increase in global average
temperature below 1.5°C. CO2 emission rates must fall by
about 45% below 2010 rates by 2030, and reach zero by around 2050. In contrast, less stringent reductions, about
20% by 2030, not reaching a zero rate until about 2070, would result in an
average temperature increase of 2.0°C.
The 1.5°C
trajectory requires “rapid and far-reaching transitions in energy, land,
urban and infrastructure (including transport and buildings), and industrial
systems”. It also necessitates development
of new technologies not yet industrialized to ensure success.
The Greenhouse Effect Was Identified in
the 1800s. The scientific understandings of the greenhouse effect, that CO2 was a
greenhouse gas, and that CO2 emissions threatened a worsening
greenhouse effect, were identified initially in the nineteenth century. Charles Keeling was the first to measure the
increase in atmospheric CO2 directly, beginning in 1958.
More recently climate scientists have understood the
threats posed by increased GHG emissions and global warming. For example, Rafe Pomerance began warning as early
as 1979, of the impending harm from continued burning of fossil fuels, but his
urgings and those of colleagues were ignored (Nathaniel Rich, New York Times
Magazine, August 5, 2018).
IPCC Assessment Reports.
The Intergovernmental Panel on Climate Change (IPCC), created under the United
Nations (UN) Environment Program and the World Meteorological Organization, has
been issuing Assessment Reports presenting scientific data and discussing
mitigation and adaptation methodologies beginning in 1990, at intervals of 5-7
years. The most recent one, the fifth,
appeared in three parts over 2013-4.
The basic conclusions throughout this series have
not wavered from those presented in the first Report; the difference over this 24-year
period has been rather that a) the number of climate scientists at work, and our
understanding of climate science based on their results, have grown dramatically;
and b) technologies that permit more extensive and more accurate gathering of
data, as well as the power to analyze large bodies of data, has likewise grown significantly. This has permitted the conclusions and
recommendations made in the Fifth Assessment Report to be offered with the
highest levels of certainty and confidence, compared to those in the previous
versions. Even so, over this interval the
world has not embraced these recommendations as energetically and as early as
would have been needed to respond to the climate crisis.
Conclusion
The IPCC Report on Global Warming of 1.5°C summons the world to take
extensive, radical and immediate actions to keep the rise in global average
temperature below about 1.5°C. Because of earlier inaction it now foresees
the need to reduce global GHG emission rates to zero by 2050. This will require committed technological
development and deployment, and the exercise of political will that reflects
scientific necessity and moral responsibility across the globe.
This transformation must account for three factors
in future global energy demand. First,
all power generation, transportation, and heating and cooling of the built
environment must be furnished from renewable sources. Second, raising the living standards of less
developed nations imposes additional demands for renewable energy. And third, the anticipated increase in the
world’s population likewise is a major source of increased energy demand.
Failure to act decisively is likely to result in worsening
climatic consequences as time passes whose effects will continue indefinitely.
Notes:
The IPCC issued this report at the direction of the
UN conference that led to the Paris Agreement on the climate in 2015.
Press Release and Headline Statements of the
Intergovernmental Panel on Climate Change for the Summary for Policymakers of
the full Report on Global Warming of 1.5°C http://www.ipcc.ch/pdf/session48/pr_181008_P48_spm_en.pdf
and http://report.ipcc.ch/sr15/pdf/sr15_headline_statements.pdf
Report in the New York Times https://www.nytimes.com/2018/10/07/climate/ipcc-climate-report-2040.html?action=click&module=Top%20Stories&pgtype=Homepage
Report in Science Magazine http://www.sciencemag.org/news/2018/10/key-climate-panel-citing-impending-crisis-urges-crash-effort-reduce-emissions
Report in Science Daily https://www.sciencedaily.com/releases/2018/10/181008075147.htm
© 2018 Henry Auer
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