Honors & Awards

  • Certificate of Achievement in Mentoring, School of Earth, Energy & Environmental Sciences, Stanford University, Stanford, CA (2016-2017)
  • Travel Award, 2016 Graduate Climate Conference, Forest Pack, WA (2016)
  • Travel Award, 2016 Severe Convection and Climate Conference, Columbia University, New York, NY (2016)
  • Travel Award, 2014 CESM Tutorial, National Center for Atmospheric Research, Boulder, CO (2014)
  • Travel Award, 2014 Fourth Workshop on Understanding Climate Change from Data, National Center for Atmospheric Research, Boulder, CO (2014)

Professional Affiliations and Activities

  • Member, Stanford Woods Institute for the Environment Rising Environmental Leaders, Stanford, CA (2015 - Present)
  • Member, American Geophysical Union (2012 - Present)
  • Member, American Meteorological Society (2012 - Present)
  • President, Chi Epsilon (2009 - 2010)
  • Member, Chi Epsilon (2008 - Present)

Education & Certifications

  • BS, North Carolina State University, Civil Engineering (2009)
  • EIT, The North Carolina Board of Examiners for Engineers and Surveyors, Civil Engineering (2009)
  • MS, North Carolina State University, Civil Engineering (2011)

Service, Volunteer and Community Work

  • Graduate Student Mentor in the Enhancing Diversity in Graduate Education (EDGE) Doctoral Fellowship Program, Stanford University (September 2016 - Present)


    Stanford, CA

  • Graduate Student Advisory Committee, School of Earth, Energy and Environmental Sciences, Stanford University (June 1, 2014 - Present)


    Stanford, CA, USA

  • North Carolina State Representative, Engineers Without Borders-USA (January 1, 2009 - December 1, 2011)


    Raleigh, NC, USA

  • Student Member, Engineers Without Borders-USA, North Carolina State University (August 1, 2005 - 12/1/2011)


    Raleigh, NC, USA

  • Coordinator for the South East Regional Workshop, Engineers Without Borders-USA (June 1, 2010 - October 1, 2010)


    Chapel Hill, NC, USA

  • Student Advisory Board, Department of Civil, Construction and Environmental Engineering (August 1, 2009 - August 1, 2010)


    Raleigh, NC, USA

Current Research and Scholarly Interests

Impacts of climate change on global drought and precipitation

Work Experience

  • Post-Master's Researcher, Oak Ridge National Laboratory (1/21/2012 - 7/1/2013)

    Research mentor: Dr. Moetasim Ashfaq
    Drought and extreme precipitation analysis, investigation of South Asian monsoon dynamics, regional climate modeling


    Oak Ridge, Tennessee, USA

All Publications

  • Quantifying the influence of global warming on unprecedented extreme climate events PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Diffenbaugh, N. S., Singh, D., Mankin, J. S., Horton, D. E., Swain, D. L., Touma, D., Charland, A., Liu, Y., Haugen, M., Tsiang, M., Rajaratnam, B. 2017; 114 (19): 4881-4886


    Efforts to understand the influence of historical global warming on individual extreme climate events have increased over the past decade. However, despite substantial progress, events that are unprecedented in the local observational record remain a persistent challenge. Leveraging observations and a large climate model ensemble, we quantify uncertainty in the influence of global warming on the severity and probability of the historically hottest month, hottest day, driest year, and wettest 5-d period for different areas of the globe. We find that historical warming has increased the severity and probability of the hottest month and hottest day of the year at >80% of the available observational area. Our framework also suggests that the historical climate forcing has increased the probability of the driest year and wettest 5-d period at 57% and 41% of the observed area, respectively, although we note important caveats. For the most protracted hot and dry events, the strongest and most widespread contributions of anthropogenic climate forcing occur in the tropics, including increases in probability of at least a factor of 4 for the hottest month and at least a factor of 2 for the driest year. We also demonstrate the ability of our framework to systematically evaluate the role of dynamic and thermodynamic factors such as atmospheric circulation patterns and atmospheric water vapor, and find extremely high statistical confidence that anthropogenic forcing increased the probability of record-low Arctic sea ice extent.

    View details for DOI 10.1073/pnas.1618082114

    View details for Web of Science ID 000400818400030

    View details for PubMedID 28439005

  • Regional atmospheric CO2 inversion reveals seasonal and geographic differences in Amazon net biome exchange. Global change biology Alden, C. B., Miller, J. B., Gatti, L. V., Gloor, M. M., Guan, K., Michalak, A. M., van der Laan-Luijkx, I. T., Touma, D., Andrews, A., Basso, L. S., Correia, C. S., Domingues, L. G., Joiner, J., Krol, M. C., Lyapustin, A. I., Peters, W., Shiga, Y. P., Thoning, K., van der Velde, I. R., van Leeuwen, T. T., Yadav, V., Diffenbaugh, N. S. 2016; 22 (10): 3427-3443


    Understanding tropical rainforest carbon exchange and its response to heat and drought is critical for quantifying the effects of climate change on tropical ecosystems, including global climate-carbon feedbacks. Of particular importance for the global carbon budget is net biome exchange of CO2 with the atmosphere (NBE), which represents nonfire carbon fluxes into and out of biomass and soils. Subannual and sub-Basin Amazon NBE estimates have relied heavily on process-based biosphere models, despite lack of model agreement with plot-scale observations. We present a new analysis of airborne measurements that reveals monthly, regional-scale (~1-8 × 10(6)  km(2) ) NBE variations. We develop a regional atmospheric CO2 inversion that provides the first analysis of geographic and temporal variability in Amazon biosphere-atmosphere carbon exchange and that is minimally influenced by biosphere model-based first guesses of seasonal and annual mean fluxes. We find little evidence for a clear seasonal cycle in Amazon NBE but do find NBE sensitivity to aberrations from long-term mean climate. In particular, we observe increased NBE (more carbon emitted to the atmosphere) associated with heat and drought in 2010, and correlations between wet season NBE and precipitation (negative correlation) and temperature (positive correlation). In the eastern Amazon, pulses of increased NBE persisted through 2011, suggesting legacy effects of 2010 heat and drought. We also identify regional differences in postdrought NBE that appear related to long-term water availability. We examine satellite proxies and find evidence for higher gross primary productivity (GPP) during a pulse of increased carbon uptake in 2011, and lower GPP during a period of increased NBE in the 2010 dry season drought, but links between GPP and NBE changes are not conclusive. These results provide novel evidence of NBE sensitivity to short-term temperature and moisture extremes in the Amazon, where monthly and sub-Basin estimates have not been previously available.

    View details for DOI 10.1111/gcb.13305

    View details for PubMedID 27124119

  • High-resolution ensemble projections of near-term regional climate over the continental United States JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES Ashfaq, M., Rastogi, D., Mei, R., Kao, S., Gangrade, S., Naz, B. S., Touma, D. 2016; 121 (17): 9943-9963
  • A multi-model and multi-index evaluation of drought characteristics in the 21st century JOURNAL OF HYDROLOGY Touma, D., Ashfaq, M., Nayak, M. A., Kao, S., Diffenbaugh, N. S. 2015; 526: 196-207
  • Anthropogenic warming has increased drought risk in California. Proceedings of the National Academy of Sciences of the United States of America Diffenbaugh, N. S., Swain, D. L., Touma, D. 2015; 112 (13): 3931-3936


    California is currently in the midst of a record-setting drought. The drought began in 2012 and now includes the lowest calendar-year and 12-mo precipitation, the highest annual temperature, and the most extreme drought indicators on record. The extremely warm and dry conditions have led to acute water shortages, groundwater overdraft, critically low streamflow, and enhanced wildfire risk. Analyzing historical climate observations from California, we find that precipitation deficits in California were more than twice as likely to yield drought years if they occurred when conditions were warm. We find that although there has not been a substantial change in the probability of either negative or moderately negative precipitation anomalies in recent decades, the occurrence of drought years has been greater in the past two decades than in the preceding century. In addition, the probability that precipitation deficits co-occur with warm conditions and the probability that precipitation deficits produce drought have both increased. Climate model experiments with and without anthropogenic forcings reveal that human activities have increased the probability that dry precipitation years are also warm. Further, a large ensemble of climate model realizations reveals that additional global warming over the next few decades is very likely to create ∼100% probability that any annual-scale dry period is also extremely warm. We therefore conclude that anthropogenic warming is increasing the probability of co-occurring warm-dry conditions like those that have created the acute human and ecosystem impacts associated with the "exceptional" 2012-2014 drought in California.

    View details for DOI 10.1073/pnas.1422385112

    View details for PubMedID 25733875

  • Near-term acceleration of hydroclimatic change in the western US JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES Ashfaq, M., Ghosh, S., Kao, S., Bowling, L. C., Mote, P., Touma, D., Rauscher, S. A., Diffenbaugh, N. S. 2013; 118 (19): 10676-10693