Biogenic VOC emissions

Trees and natural vegetation release air pollutants (biogenic), just like people (anthropogenic).

Figure from a great website by Dr. Wilson from Duke University, with lots of information.

The overall amount of this pollution can be modelled:

http://www.sciencedirect.com/science/article/pii/S1352231005000907

Its important to put this into perspective: human (anthropogenic) emissions of VOCs can be 40 times greater than the highest modelled biogenic emissions.  But the compounds plants produce may be more effective in generating hazardous compound Ozone.  Atmospheric chemistry is complex, and it is ironic that the highest biogenic pollution emissions occur in the same areas that high anthropogenic pollution also occurs, compounding the problem.  

Current data shows biosphere carbon uptake holding steady

One of the biggest questions for ecosystem scientists is the degree to which terrestrial and marine ecosystems  can continue to sequester carbon in the face of continuing human emissions of CO2 and accompanying global climate change.

This is one of the best (i.e. easiest to interpret) graphs to show that the fraction of emitted CO2 remaining in the atmosphere (i.e. not sequestered) has held steady at around 50% for the last 40+ years (purple line, "Airborne Fraction").  Data Sources: Fossil fuel CO2 emissions - Land use CO2 emissions -  Airborne CO2 levels Graph by Willis Eschenbach.

Similar conclusions were reached by the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory in Boulder, Colorado last year.

Air Ions and Indoor Air Quality

     Having researched air ions before, I can attest that the subject is extremely technical and, worse, often prone to contradiction and obscurity depending on who is writing (and who is selling) various ideas.  It is another of those interdisciplinary areas with different and competing claims, in this case, from fields as divergent as air chemistry, ecology, and human health.  The following article, from Townsend Letters, does an admirable job of introducing most of the major competing health claims and sifting the evidence:

Static Electricity and Respiratory Infections
More times than not, shaking out a blanket on a cold night generates the crackle and sting of static electricity and a flurry of sparks. Synthetic materials, low humidity, and ungrounded electrical equipment are producing an unprecedented amount of electrostatic charge indoors, and these electrical fields may be contributing to increased risk of respiratory illness and other infections, according to a 2007 article in Atmospheric Environment. Indoors, most particles, including microbes and allergens, are so small (less than 1 microgram) that they could float in the air indefinitely; but electrical charges cause these miniscule particles to settle on surfaces and stick. These surfaces include skin and lungs. High electrostatic levels and increased deposition of airborne particles on skin have been linked to facial rashes, especially when humidity is low. Charged particles in the lungs increase the risk of infection and asthma. 

Keith S. Jamieson, H. M. ApSimon, and J. N. B. Bell advocate several ways to decrease indoor static electricity and the accompanying health effects. One recommendation is to reduce electrical charges by grounding laptop computers and other electrical equipment. They also recommend unplugging equipment when it's not in use. 

Another option is bipolar air ionization. (Long-term unipolar air ionization with negative ions has shortened lifespan of laboratory animals.) Air ionizers produce varying amounts of ozone, which damages the lungs, according to the EPA. Jamieson et al. urge people to use passive air ionization measures, such as grounding electrical equipment and choosing materials and furniture finishes that do not conduct electrical charges.

Another way to combat electrostatic is to use humidifiers. Indoor heating and cooling systems often reduce humidity levels. Low humidity encourages high electrostatic levels and decreases beneficial small air ion levels. (Small air ions kill microbes and reduce employee fatigue in the office workplace.) Humidifiers are often used to make breathing easier during respiratory infections; but humidifying indoor air, especially in winter months when furnaces are running, may prevent illness as well. 

Jamieson KS, ApSimon HM, Bell JNB. Electrostatics in the environment: how they may affect health and productivity. Electrostatics 2007 Journal of Physics: Conference Series. doi:10.1088/1742-6596/142/1/012052. Available athttp://iopscience.iop.org/1742-6596/142/1/012052. Accessed September 18, 2012.
Jamieson KS, ApSimon HM, Jamieson SS, Bell JNB, Yost MG. The effects of electric fields on charged molecules and particles in individual microenvironments [abstract]. Atmosph Environ. August 2007;41(25):5224–5235. Available at www.sciencedirect.com. Accessed April 27, 2011.
Reeves D. Electrical fields from everyday equipment and materials could increase infection risk [press release]. Imperial College London. July 20, 2007. Available atwww3.imperial.ac.uk. Accessed September 18, 2012.

Variable Land Carbon Sink

b, CO2 emissions from fossil fuel combustion and cement production, and from LUC. c, Land CO2 sink (negative values correspond to land uptake). d, Ocean CO2 sink (negative values correspond to ocean uptake).

Le Quéré C, Raupach MR, Canadell JG, Marland G, others. Trends in the sources and sinks of carbon dioxide. Nature Geoscience. 2009;2(12):831–836.


"An increasing total airborne fraction implies that total sinks are increasing more slowly than total emissions, so that sinks are not keeping pace with emissions.

The CO2 growth rate also varies strongly at interannual (1 to 10 y) time scales, through mainly biophysical mechanisms. Fluctuations in CO2 growth rate correlate with the El-Nino-Southern-Oscillation (ENSO) climate mode (Keeling and Revelle, 1985; Keeling et al., 1995; Jones and Cox, 2005), because the terrestrial carbon balance in tropical regions is tilted from uptake to release of CO2 during dry, warm El-Ni ˜ no events (Zeng et al., 2005; Knorr et al., 2005).

Volcanic events are also significant: the CO2 growth rate decreased for several years after the eruption of Mt. Pinatubo in June 1991 (Jones et al., 2001), probably because of increased net carbon uptake by terrestrial ecosystems due to higher diffuse solar radiation (Gu et al., 2003) and cooler temperatures (Jones and Cox, 2001) caused by volcanic aerosols."
1. Raupach MR, Canadell JG, Le Quéré C. Anthropogenic and biophysical contributions to increasing atmospheric CO2 growth rate and airborne fraction. Biogeosciences. 2008;5(6):1601–1613.

Carbon Tracker


Fig. 1. A demonstration of how carbon flux indices [GSNF, growing season net flux; DSNF, dormant season net flux; AMP, amplitude (|DSNF – GSNF|); NCF, net carbon flux (GSNF + DSNF)] are calculated. Any month for which the net carbon flux is negative is included in the GSNF (open vertical bars). Any month for which the net carbon flux is positive is included in the DSNF (filled vertical bars). Mean 2000–2008 fluxes shown for boreal North America (a) southern Africa (b) and tropical Asia (c).

GURNEY KR, ECKELS WJ. Regional trends in terrestrial carbon exchange and their seasonal signatures. Tellus B.

Fig. 2. Comparison of decadal mean net carbon flux for individual land regions. Black cross symbols (X) denote the mean of 13 TransCom 3 models, open circle symbols (O) denote mean of the three S07 TransCom 3 models, individual model estimates within the S07 average are denoted by a filled square, circle and triangle. Vertical error bars represent the total 1σ flux uncertainty (quadrature sum of model spread and the root mean square of individual model posterior uncertainty) associated with the mean of the 13 TransCom 3 models. (c) 2000–2008 mean net carbon flux.

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 2.8.5.7), which is consistent with the general ineffectiveness of high clouds in influencing diurnal surface temperatures (Hansen et al., 1995, 2005). " (IPCC 2007)

Maps of the Upper Atmosphere

Ship Pollution

Large ships continue to use old, polluting diesel engines, with disasterous health effects for people living close to the ocean. The EPA's proposed plan would greatly alleviate this largely unregulated source of pollution, which is currently equal to about 120 coal power plants running continuously in our nation's harbors and waterways. (source: President's Cancer Commission report, 2010)

EPA Website on large ship pollution.

Interestingly, ships also affect cloud formation: the soot in their exhaust creates nuclei for water droplets to condense and form clouds: http://earthobservatory.nasa.gov/IOTD/view.php?id=44517