Wednesday, April 20, 2011

Weather Prediction: Accuracy and Skill

type weather text here

For a huge database of historical comparisons between the model predictions and observed weather: or

For comparisons of the various model runs:

Wednesday, April 13, 2011

Terrestrial Fertilization to Sequester CO2?

One of the main uncertainties in the global carbon cycle is measuring the amount of carbon bound up in ecosystems such as forests and grasslands. This Net Ecosystem Production (NEP) converts CO2 to plant material, detritus, and some animals. Most escapes back to the atmosphere as respired CO2, but some is sequestered in soil organic matter and trees.

Most ecosystems are Nitrogen limited because fertilization with nitrogen increases NEP. Interestingly, many ecosystems are already fertilized by Nitrogen deposition from drifting clouds of various nitrogen compounds emitted by urban areas, industry, and agriculture.

Nitrogen deposition increases productivity and decreases respiratory losses from decomposition (Hogberg). But how much? And how much is too much? Natural vegetation may be satiated/saturated with a low quantity of nitrogen, and any more would begin acidifying the soil, killing plants and washing away to pollute the watersheds.

Magnani et al attempt to answer some of these questions and measure the size of the "The human footprint in the carbon cycle of temperate and boreal forests" of Europe. They find that the amount of nitrogen deposited in European forests confers a huge increase in fertility; they find no sign of a decrease due to Nitrogen saturation.

However, their findings rested on a number of unpublished studies, and a flurry of correspondence questioned their main conclusions. De Shrivjer et al point out that just because NEP continues to increase with increasing Nitrogen deposition, this doesn't mean that the forest ecosystems aren't loosing nitrogen as runoff. Indeed, it makes sense that at very high applications of fertilizer an increasing fraction would be wasted. Many farmers have to contend with the problem that, beyond a certain point, a doubling of Nitrogen fertilizer may confer only an incremental increase in crop productivity, while vastly increasing the amount of Nitrogen that washes off.

de Vries present a more central problem in Magnani et al's results: according to Magnani's data correlation, for every unit of Nitrogen applied to European forests, 470 units of carbon are sequestered. Yet the only plant material with a C:N ratio that high is pure xylem wood, and it seems unlikely that all of the deposited nitrogen is being used to grow tree stems. Furthermore, de Vries et al find that Magnani et al failed to control for a range of other variables that could affect forest NEP. de Vries reanalyze that portion of Magnani's data that is publicly available and find a more plausible -- and vastly reduced -- C:N ratio of 20 to 40 (20-40 units carbon for every unit nitrogen).

It doesn't end there, though. Magnani et al respond that they agree with De Shrivjer, but refute de Vries. Magnani point out differences between wet and dry deposition, to argue that their stoichiometric ratio is really closer to 175-225. They claim that this ratio is not implausible, even though it is much higher than actual forest fertilization experiments (Nadelhoffer). They explain this difference by suggesting that up to 70% of the actual nitrogen deposited is absorbed by leaves, whereas the forest fertilization experiments applied nitrogen to the soil. (Nadelhoffer).

{[It is not clear to me what the consensus is on how much nitrogen can be absorbed by the canopy, or why wet versus dry deposition matters. }

News and Views: Hogberg P. Environmental science: Nitrogen impacts on forest carbon. Nature. 2007 June 14;447(7146):781-782.
Original Paper: Magnani F, Mencuccini M, Borghetti M, Berbigier P, Berninger F, Delzon S, Grelle A, Hari P, Jarvis PG, Kolari P, et al. The human footprint in the carbon cycle of temperate and boreal forests. Nature. 2007 June 14;447(7146):849-851.
Questions: De Schrijver A, Verheyen K, Mertens J, Staelens J, Wuyts K, Muys B. Nitrogen saturation and net ecosystem production. Nature. 2008 February 14;451(7180):E1.
More Questions: de Vries W, Solberg S, Dobbertin M, Sterba H, Laubhahn D, Reinds GJ, Nabuurs G-J, Gundersen P, Sutton MA. Ecologically implausible carbon response? Nature. 2008 February 14;451(7180):E1-E3.
Response:Magnani F, Mencuccini M, Borghetti M, Berninger F, Delzon S, Grelle A, Hari P, Jarvis PG, Kolari P, Kowalski AS, et al. Magnani et al. reply. Nature. 2008 February 14;451(7180):E3-E4.
More Information: Nadelhoffer, K. J. et al. Nitrogen deposition makes a minor contribution to carbon sequestration in temperate forests. Nature 398, 145–148 (1999)
Follow Up: SUTTON MA, SIMPSON D, LEVY PE, SMITH RI, REIS S, Van OIJEN M, De VRIES WIM. Uncertainties in the relationship between atmospheric nitrogen deposition and forest carbon sequestration. Global Change Biology. 2008 September 1;14(9):2057-2063.

Tuesday, April 12, 2011

EPA Pollution Standards

EPA Where You Live


Drinking Water

Antarctic Ice Increasing?

Most of this post deals with a paper by Turner, 2009.

My confusion started with a Watts Up With That post claiming that Antartica is actually gaining sea ice. As usual, a SkepticalScience page attempts a refutation, but to do so has to get into some complicated details.

So what is the trend?


But Antartic sea ice is formed by a number of factors, including UV radiation from the hole in the Ozone layer, and land ice has been decreasing:"Ozone levels over Antarctica have dropped causing stratospheric cooling and increasing winds which lead to more areas of open water that can be frozen"

Apparently, land ice is more important in Antartica, and this had been decreasing. If the Ross Ice sheet collapsed, as it has numerous times in past interglacials, it would raise sea level by 21 feet.

Climate Change: Contrails

Aircraft Contrails Stoke Warming (Reuters, ):"Aircraft condensation trails criss-crossing the sky may be warming the planet on a normal day more than the carbon dioxide emitted by all planes since the Wright Brothers' first flight in 1903, according to a study in Nature Climate Change." [This is about 0.025 Watts per square meter, according to the IPCC (2007)]

Citation: Ulrike Burkhardt & Bernd Kärcher Global radiative forcing from contrail cirrus. Nature Climate Change 1, 54–58 (2011)

Image from Earth Observatory: "NASA scientists have found that cirrus clouds, formed by contrails from aircraft engine exhaust, are capable of increasing average surface temperatures enough to account for a warming trend in the United States that occurred between 1975 and 1994."
Citation: Minnis, Patrick, J. Kirk Ayers, Rabindra Palikonda, Dung Phan, 2004: Contrails, Cirrus Trends, and Climate. J. Climate, 17, 1671–1685.

"Trends in cirrus coverage and 300-hPa relative humidty (1971-19995) and estimated 1992 linear congtrail coverage. (a) Trends in cirrus coverage for all regions with more than 15yr of data. (b) Subset of (1) for all regions having trends sinifcant at the 90% confidence level according to Student's t test. (c) Estimated linear contrail coverage...Only observations taken from land stations and from ships are used for the land and ocean air traffic regions, respectively. (d) Trends in annual mean NCEP relative humidity at 300 hPa."

Citation: Minnis, Patrick, J. Kirk Ayers, Rabindra Palikonda, Dung Phan, 2004: Contrails, Cirrus Trends, and Climate. J. Climate, 17, 1671–1685.

"In response to the Minnis et al. conclusion, contrail Radiative Forcing (RF) was examined in two global climate modelling studies (Hansen et al., 2005; Ponater et al., 2005). Both studies concluded that the surface temperature response calculated by Minnis et al. (2004) is too large by one to two orders of magnitude. For the Minnis et al. result to be correct, the climate efficacy or climate sensitivity of contrail RF would need to be much greater than that of other larger RF terms, (e.g., CO2). Instead, contrail RF is found to have a smaller efficacy than an equivalent CO2 RF (Hansen et al., 2005; Ponater et al., 2005) (see Section, which is consistent with the general ineffectiveness of high clouds in influencing diurnal surface temperatures (Hansen et al., 1995, 2005). " (IPCC 2007)

Monday, April 11, 2011

Best Periodic Table Ever

I've been on the lookout for the best periodic table for a couple months now, and have finally found it. Various versions can be downloaded here. An explanation of the new format.

Physiological Toxicology

Different toxic compounds come to rest in different organs and regions of the body, depending on their mode of transport in the human body. For example, many toxins are "mistaken" for similar compounds, and stored accordingly. Polyaromatic hydrocarbons (PAHs) are fat soluble and look like cholesterol, so they are stored in fat deposits. Lead "looks like" calcium, so it is stored in the bones.

Friday, April 08, 2011

Climate Crunch

Deconstructing Conclusions
During the winter of 2009-2010 I began investigating climate science, and since then have been reading in the field on-and-off. Again this last winter I have been reading way too much, trying to get to the bottom of various intricacies of the coupled earth-human system. Suffice to say, the Earth's climate is extremely complex, and every scientific sub-discipline has made its own peace with the devil in the details. Getting to the bottom of what scientists believe, and why, is no easy task, and after more than a year of research I have learned a huge amount about the Earth, but still am not definitively convinced about every aspect of climate change science.

This is as it should be. Science is complex and ever-evolving, and the Earth is a very, very complicated place. But provisional results and untested assumptions, although ever-present, make soft bedrock for climate policy. The truth is that we simply do not understand many of the key issues, such as feedbacks, in the climate system.

Many issues, such as divergence in tree-ring proxy records, don't by themselves discredit the theory of anthropogenic global warming, even if scientists can't explain everything. But they do begin to cast doubts. The issue of "hide the decline" probably falls into this category, because although some scientists chose to substitute instrument data for the misbehaving paleo data, the divergance can be explained. But is this explanation just hand-waving? How do we really know what happened hundreds or thousands of years ago? Obviously climate proxies may be complicated, idiosyncratic, and only reliable under certain conditions. It has been said that "trees are not thermometers," but this admission, even if carefully defined, can lead to increasing skepticism.

Unresolved Issues
Skeptic Science (SkS) has a great index of skeptic arguments, many of which continue to be problematic. They attempt to "refute" each argument, and they are the best source for good answers to most of these issues. But not every question can be answered definitively. Sometimes one question simply leads to three or four more. For example, they point out that warming is not due to the sun....but it is very, very, complicated. SkS explains why CO2 lags temperature in paleoclimate....but their response is not good system thinking, doesn't address the skeptic arguments about what the Vostok ice core means, and isn't especially convincing.

I've been researching climate change for over a year, and still am not close to understanding many of the major issues. What's worse, I can't find good evidence that the climate scientists understand all of the issues either! Much of science is dependent on good faith and trust, but at some point an explanation has to be convincing. Some theories (and I would put String Theory and Global Warming into this category) are too gnarly to be comprehended by mere mortals. They may be true, but I can't believe in what I don't understand.

The bottom line is that, if you really want to know,... its complicated. I'm officially revoking my previous conclusion, pending better explanations of the science. Maybe I'll have to wait to believe the models until they're proved true: until then I'll continue to entertain belief in multiple possibilities about this weird, beautiful world we live on.

More Paleoclimate Links: