The Weekly Carboholic: Climate disruption lowering Juneau sea level

Posted on May 19, 2009




There’s a few reasons that I prefer the phrase “climate disruption” over “global warming” or even “climate change.” One of those reasons is that “climate disruption” describes what’s happening around the world in a way that people immediately understand – the climate they’ve grown accustomed to is going to be disrupted in some fashion, but not necessarily in a way that’s immediately obvious. One place that’s historically warm and wet could turn hot and even wetter (something that might reasonably be predicted by your average climate layperson) while another area could actually cool off and dry out as a result of climate disruption. The effects of climate disruption may be counter intuitive, thus the term “disruption.”

One such place that is facing a counter intuitive disruption is Juneau, the state capital of Alaska. As local glaciers melt rapidly, the sea level around the city is actually falling instead of rising.

The NYTimes article explains the basic process like this – when you melt off billions of tons of water ice from glaciers around Juneau, the land rebounds similarly to how a couch cushion rebounds when you stand up. In this case, the earth is rebounding faster than the sea level is rising, and so the local sea level is effectively dropping. In the town of Gustuvus, about 40 miles to the northwest of Juneau, the land is rising about three inches per year, the fastest rate of rebound in North America.

As a result of the lower sea level around Juneau, the NYTimes article points out that there could be wetlands lost, salmon runs could dry out, a formerly navigable channel is impassable to boats at low tide, and Douglas Island is in the process of becoming a peninsula.

Of course, if there’s a place where the local sea level is falling instead of rising, then there will also be places where the local sea level rises even more than the global average – like along the east and west coasts of the United States….


Paper shows cooler periods entirely expected

coolingIn late April, David Easterling of the National Climatic Data Center (NCDC) and Michael Wehner of the Lawrence Berkeley National Laboratory published a paper titled “Is the climate warming or cooling?” This paper represents an attempt by the authors to provide a peer-reviewed counterargument to climate disruption deniers who claim that the statistically insignificant warming since 1998 show that global warming is over.

It’s true that there has been no statistically significant warming since 1998. But this isn’t a statistically meaningful result. First, there was an unusually strong el Nino in 1998 that made that year unusually hot. In 2008 and thus far through 2009 there’s been la Nina conditions that have made the last year or so colder. And as a result, a statistical least-squares fit of a line to the data would be expected to show little warming for the last decade. But as the paper’s authors point out, if you choose 1999 as your starting point, all of a sudden there’s statistically valid warming again.

The problem, says the paper, is that natural variability is added atop the carbon dioxide (CO2) driven warming signal. And when that natural variability is greater on short time scales than the CO2 signal, then it’s all but inevitable that there will be decades where warming appears to stop only to start up again later. This is illustrated in the figure above for two periods in a single model run.

It’s a misconception that the Earth’s climate will warm perpetually without any variability – the real climate doesn’t work like that. Instead, the misconception is probably a result of poor communication about the differences between model averages (which intentionally smooth out the variability seen in the image above in order to discover underlying trends) and the results of a single model run. The Earth’s actual climate response is going to appear much closer to a single model run, with all the attendant peaks and valleys, than to any multiple model average.

The authors also analyzed the statistical significance of positive vs. negative trends in models and the measured data and found that even when negative trends existed in the model results, 0.0% of the negative trends were statistically significant to the 95% confidence interval. On the other hand, 26.0% of positive trends were statistically significant at the same confidence interval. This means that even when the models show negative trends, the trends are so small as to be effectively meaningless.

As the authors say, “it is reasonable to expect that the natural variability of the real climate system can and likely will produce multi-year periods of sustained “cooling” or at least periods with no real trend even in the presence of long-term anthropogenic forced warming.


Convert biomass to electricity instead of ethanol

A new paper in the journal Science concludes that combusing biomass into electricity (bioelectricity) is more efficient than conversion into ethanol for combustion in automobile engines. Gross transportation output per hectare was 85% greater for bioelectricity than for ethanol and net output (subtracting out the life cycle costs of the vehicle itself) was 56% greater for bioelectricity than for ethanol.

The main reason? Internal combustion engines are woefully inefficient compared to electric motors.

While these are impressive results, the paper points out that the cost effectiveness of biomass conversion into either electricity or ethanol depends on the costs of competing electricity generation methods and petroleum. In addition, the calculations reported in the paper don’t automatically assume that bioelectricity is still the better method given systemic effects of “regional water resources, battery toxicity and recycling, air pollution,” etc.

Once those other effects are factored in, however, the end analysis may well show that the internal combustion engine must either fade away or find ways to become radically more efficient in a green transportation future.

Image credits:
Climate Change: Predicted Impacts on Juneau, Figure 26
NYTimes, from Geophysical Research Letters paper

Posted in: Uncategorized