The answer appears to be yes.
The 2005 National Research Council report on page 96 specifically stated the following,
“Several nonradiative forcings involve the biological components of the climate system”
with one type of summarized as,
“Biogeochemical forcing involves changes in vegetation biomass and soils. For example, increased nitrogen deposition caused by greater anthropogenic emissions of ammonia (NH3), nitric oxide (NO), and nitrogen dioxide (NO2) is a biogeochemical forcing of the climate system (Holland et al., 2005; Nitrogen deposition onto the United States and Western Europe: A synthesis of observations and models. Ecological Applications, 15, 38-57). This deposition has altered the functioning of soil, terrestrial vegetation, and aquatic ecosystems worldwide. Galloway et al. (2004; Nitrogen cycles: Past, present and future. Biogeochemistry 70:153-226). document that human activities increasingly dominate the nitrogen budget at the global scale and that fixed forms of nitrogen are accumulating in most environmental reservoirs.”
This biogeochemical forcing results in significant alterations in the physical components of the climate system such as the surface albedo, and the partioning of atmospheric turbulence into sensible and latent heat components, which subsequently affects all other aspects of the climate system
A seminar was presented October 6, 2005 at Colorado State University that summarized the current knowledge of nitrogen deposition, The informative abstract is,
“Using Observations and Models to Understand Biosphere-Atmosphere
Nitrogen and Sulfur Cycles
by Elisabeth A. Holland
NCAR Atmospheric Chemistry Division
The global nitrogen cycle has been profoundly perturbed during the industrial era through fossil fuel combustion and agricultural intensification. The atmospheric deposition networks designed to address the impact of acid rain deposition onto rural and remote areas in the some most industrialized regions of the world provides a key data set with adequate temporal and spatial coverage to understand the changing global nitrogen cycle. The measurements were made by the National Atmospheric Deposition Program and National Trends Network (NADP/NTN) and European Monitoring for the Environment Programme (EMEP).
To construct continental scale N budgets, we produced maps of N deposition fluxes from site-network observations for the US and Western Europe. The maps and analyses are necessarily restricted to the network measured quantities and consist of statistically interpolated fields of aqueous NO3- and NH4+, gaseous HNO3 and NO2 (in Europe), and particulate NO3- and NH4+. Western Europe receives five times more N in precipitation than the conterminous US. Estimated N emissions exceed measured deposition in the US by 5.3-7.81 Tg N. In Europe, estimated emissions better balance measured deposition, with an imbalance of between -0.63 to 2.88 Tg N suggesting that much of the N emitted in Europe is deposited there. Taking the imbalances in the two regions, more 50% of the N emitted in the US is exported from the continent, and some of the exported N may fall on Western Europe.
We examined the 25 year record of precipitation removal of a atmospheric nitrogen, ammonium and nitrate, using a seasonal trend LOESS statistical approach . On a continental scale for both the US and Western Europe, there was little overall trend in ammonium or nitrate wet deposition. The lack of a clear trend suggests that the emissions of ammonia and nitrogen oxides over the time period between 1978 and 2003 have been relatively constant. By contrast, sulfur dioxide deposition has decreased by as much as 50% over the same time period. There has been a clear difference in the effectiveness of a series of Transboundary Air Pollution Agreements and Clean Air Acts targeting the emissions of sulfur and nitrogen oxides. The Clean Air Acts have been successful at reducing sulfur dioxide emissions but have not been successful at reducing nitrogen oxide emissions.
These spatially and temporally explicit N deposition budgets and N and S trend analyses provide key tools for verifying regional and global models of atmospheric chemistry and transport, and represent critical inputs into terrestrial models of biogeochemistry.”
The modeling of the influence on long-term weather due to nitrogen deposition is in its early infancy. However, even now it needs to be recognized that this non-radiative biogeochemical climate forcing must be accounted for in any assessment of the relative and absolute role of the diversity of different human climate forcings.
“However, even now it needs to be recognized that this non-radiative biogeochemical climate forcing must be accounted for in any assessment of the relative and absolute role of the diversity of different human climate forcings.”
Roger, first of all, doesn’t this N deposition (as distinct from the emission that leads to it) fit the very definition of a second-order forcing as it is stated to be a consequence of first-order forcings (fossil fuel burning and agricultural activities)?
Second, forcing on what? If N is a factor in acid rain, that’s very interesting and certainly part of climate, but not terribly relevant to the debate about global warming. Do the climate models even incorporate forcings that are unrelated to temperature? What did you mean by “long-term weather”?
Comment by Steve Bloom — October 12, 2005 @ 9:19 pm
Sorry I didn’t spot this in time to include in my first comment, but I note that there is one more sentence at the end of the NRC report paragraph you cited:
“In addition to impacts on ecosystem functioning, which are important in themselves, this forcing modifies physical components of the climate system, such as surface albedo and sensible and latent heat.”
This definitely seems to refer to a possible effect on temperature, but it sounds like a potentially trivial one. Dr. (?) Holland’s captioned statement didn’t make reference to any such thing; did her (subscription blocked, unfortunately) paper?
A little time spent on Google Scholar indicates that Dr. Holland at one time thought that N deposition was the answer to the “missing carbon sink,” but that view rapidly became controversial and may have been superceded (although it’s a little hard to tell just from abstracts). Does she still think so? The NRC report appears to make no reference to the idea, which is perhaps significant.
In any event, the effect of N deposition on “surface albedo and sensible and latent heat” just doesn’t sound significant absent some kind of analysis to the contrary.
Comment by Steve Bloom — October 12, 2005 @ 10:05 pm
Steve-thanks for commenting. Nitrogen deposition effects surface air temperature (and other weather variables) since it generally results in greater plant growth (it is a fertilizer). In terms of above ground leaf area, there is a greater surface to transpire water.
Thus, as one effect, there is a different portioning of latent and sensible turbulent heating of the atmosphere, as shown in Pielke Sr., R.A., 2001: Influence of the spatial distribution of vegetation and soils on the prediction of cumulus convective rainfall. Rev. Geophys., 39, 151-177.http://blue.atmos.colostate.edu/publications/pdf/R-231.pdf. The surface albedo is also changed. The result, as discussed in that paper, is a significant alteration in regional surface air temperatures, at least for grasslands, as we documented in Hanamean, J.R. Jr., R.A. Pielke Sr., C.L. Castro, D.S. Ojima, B.C. Reed, and Z. Gao, 2003: Vegetation impacts on maximum and minimum temperatures in northeast Colorado. Meteorological Applications, 10, 203-215. http://blue.atmos.colostate.edu/publications/pdf/R-254.pdf.
On the effect of nitrogen deposition on the “missing carbon sink”, there certainly is enhanced carbon assimilation since the plants grow more. Whether this accumulation continues for decades is a topic of considerable research which we are also involved in.
Comment by Roger Pielke Sr. — October 13, 2005 @ 8:23 am