Predicting Climate Change Impacts – Quotes From The Experts


annual averag precipitation for the 21st century

Yesterday at the annual Science (AAAS) meeting here in Chicago, a panel of climate experts convened for a symposium to present their research and discuss the risks and challenges facing the science as it seeks to model and predict climate changes — such as the probability of “extreme events” — due to global warming over the next decade, and beyond.

The symposium was entitled ‘Research Challenges in Climate Change: What’s New and Where Are We Going?’ The panel was comprised of renowned climate science experts and included Don Wuebbles (University of Illinois, Urbana-Champaign), Ben Kirtman (University of Miami), Michael Wehner (Lawrence Berkeley National Laboratory), Peter Clark (Oregon State University), Noah Diffenbaugh (Standford University), and Chris Field (of the Stanford Woods Institute). The last expert was actually filling in for scheduled speaker Rosina Bierbaum (University of Michigan, Ann Arbor) who, ironically, was unable to attend due to the extreme weather conditions affecting the East Coast of the US.

The following is a summary/encapsulation of some of the main points, research results and most memorable quotes from the symposium.

The Pace & Variability of Climate Change

Explaining that the rate and variability of climate change is the result of a combination of natural variability and anthropogenic forcings, Don Woebbles notes:

“We expect that there are going to be periods of time when warming is slow, weak, or even zero…and there will be times when warming is fast, strong, and non-zero.”

The Weather vs. The Climate

Explaining the distinction between the two phenomena, Ben Kirtman states:

“Weather is the ‘noise’ in the climate…We live in the noise.”

On Rare Weather Events

Addressing the apparent increase in extreme weather events, Kirtman also notes, counter-intuitively, that “Cold events warm more than warm events” and goes on to say:

“Today’s rare hot events will become common place…[and] rare events [in the future] will be progressively hot events.”

Elaborating on this point, Kirtman notes that such “rare events” (i.e., extreme weather events) are “not as rare as they used to be” and his research shows that by the year 2040, such rare events will occur “almost all the time”…and “our summers will be like Europe in 2003” (one of the hottest, driest summers on record, and which sparked immense, long-lasting wild fires).

Balancing this, Kirtman also foresees a “shift to more intense individual storms” — primarily due to variable precipitation.

On the Global Mean Rise in Sea Levels

Peter Clark – one of the two lead authors of the 5th IPCC report’s Chapter 13, entitled ‘Sea Level Rise’ — brings us up to date on the most recent and advanced climate model projections of what’s known as the global mean sea level rise (GMSLR). Clark  notes that predictions of SLR are based upon a combination of proxy indicators (such as sediment samplings from swamps and marshes), direct observations and measurements (such as glacial out flows from Greenland and Antarctica) and computer modeling. Clark observes that, based upon proxy indicators, the “rate of SLR is larger than the previous 2 million years”…with this increase growing from “about 10 millimeters per year, to nearly 100 mm/yr” over the coming decades — based upon a combination of this data and computer models. This increase, Clark notes, is most likely due to a “substantial anthropogenic contribution” (of greenhouse gases) since the 1970’s.

Clark stated the results of this predictive modeling with “high confidence” — based upon combined  measurements of thermal expansion (the general change in ice volume in response to an increase in temperature), ice sheet mass balance (specifically, from Greenland) and land water storage — but claims “medium confidence” looking just at glacier out flow (reflecting some uncertainty and variability in these measurements). Based upon all climate forcing scenarios — known as representative concentrated pathways (RCPs*) — Clark observes  “GMSLR will likely exceed that observed during the time period from 1971 to 2010” and that the rise in seal level “will be comparable to the SLR in the last Ice Age.”

Concerning the possibility of an “Antarctic collapse” Clark acknowledge that there is “no way to quantify the timing or magnitude of this impact on GMSLR” but notes that barring this collapse, models suggest medium confidence that Antarctic marine-based sectors will contribute to a rise in GMSLR of “not above a few tenths of a meter.”

However, Clark ended his presentation with a sobering observation concerning attempts to mitigate any sea surface temperature increase:

“Even if we stabilize mean surface temperatures, this will not stabilize SLR” and that it is a “virtual certainty [that] GMSLR will continue to rise for many decades past the 21st Century.”

What About Geoengineering?

This author asked the panel their opinions on geoengineering strategies to mitigate or stop severe climate change.

Noah Diffenbaugh responded by first noting that their are two main strategies here: CO2 removal (known as carbon capture and sequestration) and solar radiation management. The former strategy he called “slow and low risk” while the latter was “fast and high risk.” Diffenbaugh was critical of the view that essentially says “Let’s do it short-term to control melting ice in the Arctic” noting the great risk since we “don’t understand even a limited impact of such a strategy.”

Nevertheless, no one on the panel rejected geoengineering outright, but instead argued for a “fact-based” approach to geoengineering strategies. This is tricky thing in that there is very little experimental evidence to support any geoengineering solution (given the size of the object of engineering, that is, an entire planet).

Interestingly, none of the panelist expressed great concern that permafrost “melting” (actually, thawing) in the Arctic would lead to a significant increase in atmospheric CO2 or methane and lead to a “run-away greenhouse effect” — seeming to counter the hype over this issue in the science press.

Tackling the Human-Caused Climate Change Challenge

In ending the symposium, Don Wuebbles addressed the troubling delay in the US on climate change action — noting his deep concern for the future world his grand children would encounter — and expressed his sincere hope:

“Ar some point we are going to wake up and take on this problem seriously.”

And Chris Field observed:

“The longer we wait, the harder the problem gets to solve, the more money it will take, and the more likely we are to be unsuccessful…and mess up.”

* RCP scenarios are based upon increasing radiative forcing, measured in watts per square meter; thus each scenario (RCP 2.6, 4.5, 6.8, etc.) refers to increasing forcing due to ever-warming atmospheric temperatures (as CO2 ppm increases), with each RCP representing a more drastic/severe climate scenario.

TOP IMAGE: Based on NOAA (2007) public-domain source: This world map shows the change in annual average precipitation projected by the GFDL CM2.1 model for the 21st century. The change is in response to increasing atmospheric concentrations of greenhouse gases and aerosols based on a “middle of the road” estimate of future emissions. Future emissions are based on the “A1B” emissions scenario, taken from the Special Report on Emissions Scenarios. For the “A1B” emissions scenario, atmospheric carbon dioxide levels are projected to increase from 370 to 717 ppm. The plotted precipitation differences were computed as the difference between the 2081 to 2100 twenty year average minus the 1951 to 2000 fifty year average. Blue areas are projected to see an increase in annual precipitation amounts. Brown areas are projected to receive less precipitation in the future. (Note the irregular color bar intervals.). SOURCE: NOAA via wikipedia

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