Letters continued
sixth factor, completely neutral prior to
2001, that causes a drop in global temperatures from 2000 to 2009?
Jason J. Beckwith
new york
Susan Woerner responds:
I appreciate all of the letters, comments, and interest in the topic of climate
change. The purpose of the two articles
was to raise awareness and promote discussion of an important issue for us both
professionally and personally. It’s good to
see that we have succeeded in that regard.
Contingencies’ graphic designers did a
good job of creating the chart that combines observed temperatures, natural
forcings, and anthropogenic plus natural
forcings into a single graph. Similar information is presented in the technical
summary section of the 2007 IPCC report
referenced in the article. In particular,
the IPCC report states, “The observed
pattern of tropospheric warming and
stratospheric cooling is very likely due to
the influence of anthropogenic forcing,
particularly that due to greenhouse gas
increases and stratospheric ozone depletion.” (Note that the IPCC report defines
the term “very likely” as an assessed
likelihood of greater than 90 percent
probability of occurrence.)
While correlation isn’t causality, it does
point to the possible role humans may be
playing in the rising carbon dioxide levels
in the atmosphere. Certainly, anthropogenic forcing isn’t responsible for all of the
carbon dioxide in the atmosphere. Carbon
dioxide has been part of the earth’s atmosphere for millions of years before the
first hominid exhaled. As mentioned in
my article, most of the current increase in
warming is not due solely to humans, but
we may be adding just enough to upset a
precariously balanced system.
Recently, the Financial Times reported that Bjorn Lomborg, a well-known
and influential climate-change skeptic,
has switched his position to support a
drive to halt rising world temperatures.
Whether humans and/or some yet-un-known factor are responsible for the
rising carbon dioxide levels, the need to
address climate change as an important
risk management and adaptation issue
is undiminished. Regardless of an individual’s beliefs on the topic of climate
change, ongoing research will continue
to promote a more evidence-based approach to the topic.
