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M Z Jacobson

Publications and source records attributed to M Z Jacobson.

5 recordsLinked to original sources
PubMed2005

Enhanced coagulation due to evaporation and its effect on nanoparticle evolution.

A new explanation for the evolution of particles near a roadway is proposed. The explanation starts with data that suggest that small (<15 nm) liquid nanoparticles shed semivolatile organics (<C24) almost immediately upon emission. It is shown here that the shrinking of these particles enhances their rates of coagulation by over an order of magnitude, and this appears important in helping to explain particle evolution further downwind, as measured by two datasets, including one reported here, and as found with a three-dimensional numerical model used to simulate the data. Enhanced coagulation in isolated emission puffs may also affect evolution. Neither condensation, complete evaporation, coagulation alone, nor preferential small-particle dilution appears to explain the evolution.

Air Pollutants↗
PubMed2005

Cleaning the air and improving health with hydrogen fuel-cell vehicles.

Converting all U.S. onroad vehicles to hydrogen fuel-cell vehicles (HFCVs) may improve air quality, health, and climate significantly, whether the hydrogen is produced by steam reforming of natural gas, wind electrolysis, or coal gasification. Most benefits would result from eliminating current vehicle exhaust. Wind and natural gas HFCVs offer the greatest potential health benefits and could save 3700 to 6400 U.S. lives annually. Wind HFCVs should benefit climate most. An all-HFCV fleet would hardly affect tropospheric water vapor concentrations. Conversion to coal HFCVs may improve health but would damage climate more than fossil/electric hybrids. The real cost of hydrogen from wind electrolysis may be below that of U.S. gasoline.

Air Pollution↗
PubMed2001

Strong radiative heating due to the mixing state of black carbon in atmospheric aerosols.

Aerosols affect the Earth's temperature and climate by altering the radiative properties of the atmosphere. A large positive component of this radiative forcing from aerosols is due to black carbon--soot--that is released from the burning of fossil fuel and biomass, and, to a lesser extent, natural fires, but the exact forcing is affected by how black carbon is mixed with other aerosol constituents. From studies of aerosol radiative forcing, it is known that black carbon can exist in one of several possible mixing states; distinct from other aerosol particles (externally mixed) or incorporated within them (internally mixed), or a black-carbon core could be surrounded by a well mixed shell. But so far it has been assumed that aerosols exist predominantly as an external mixture. Here I simulate the evolution of the chemical composition of aerosols, finding that the mixing state and direct forcing of the black-carbon component approach those of an internal mixture, largely due to coagulation and growth of aerosol particles. This finding implies a higher positive forcing from black carbon than previously thought, suggesting that the warming effect from black carbon may nearly balance the net cooling effect of other anthropogenic aerosol constituents. The magnitude of the direct radiative forcing from black carbon itself exceeds that due to CH4, suggesting that black carbon may be the second most important component of global warming after CO2 in terms of direct forcing.

Aerosols↗