Understanding and Reducing the Uncertainty Associated With the Effect of Atmospheric Particles on Clouds and Climate

EPA Grant Number: F6B10683
Title: Understanding and Reducing the Uncertainty Associated With the Effect of Atmospheric Particles on Clouds and Climate
Investigators: Pierce, Jeffrey
Institution: Carnegie Mellon University
EPA Project Officer: Michaud, Jayne
Project Period: September 1, 2006 through August 31, 2008
Project Amount: $74,172
RFA: STAR Graduate Fellowships (2006) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Fellowship - Chemical Engineering , Global Climate Change


The effect of atmospheric particles generated by humans on the amount of sunlight that passes through clouds is thought to cool the atmosphere, but the magnitude of this effect is highly uncertain, largely due to the number and nature of particles in the atmosphere not being well understood. The uncertainty in this effect prevents a complete understanding of how our climate is changing. My goal is to determine the effect that human-generated particles have on the overall number of particles on which clouds may form. Additionally, I will explore the uncertainty in the concentrations of particles in the atmosphere and recommend ways to reduce the uncertainties.


I will reach my objective in three phases. First, I will explore the probability that new particles in the atmosphere will grow large enough to affect clouds through a model of particle physics. This will determine where in the atmosphere it is likely that human-generated particles may affect clouds. Second, I am going to refine the estimates of new particle emission and formation in a global atmospheric model of particle physics. Third, I am going to use the information from the first two phases to evaluate the effect of human-generated particles on clouds and climate and present the uncertainties associated with it.

Expected Results:

I predict that human-generated particles have modified clouds and cooled climate, somewhat masking the effect of greenhouse gases and that these particles have also modified the amount of sunlight reaching the ground, changing the thermodynamic cycles in the atmosphere. With a more complete understanding of these processes, we can determine how reduction in the number of particles due to EPA particulate matter regulation may affect the climate.

Supplemental Keywords:

climate change, atmospheric particles, atmospheric aerosols, cloud reflectivity, global climate modeling,, RFA, Scientific Discipline, Air, climate change, Air Pollution Effects, Environmental Monitoring, Atmospheric Sciences, Atmosphere, air quality modeling, particulate matter, anthropogenic stress, particle physics model, global change, greenhouse gases, climate models, Global Climate Change, ambient air pollution

Progress and Final Reports:

  • 2007
  • Final