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October, 2013

Global Variations in Precipitation and Water Vapor with Climate Change and
Associated Impacts to Human Health; Data Gaps and Opportunities

By L. DeWayne Cecil, Ph.D., Chief Climatologist, Global Science & Technology, Inc. (GST)

Contact: DeWayne.Cecil@gst.com


This is the first in a series of position papers describing applications of climate data and information to a variety of applications for decision support and societal benefit. The purpose of this series of papers is to begin discussion of our state of knowledge of climate change impacts to targeted sectors across society with the goal of improving human responses, adaptation, and planning. These papers are not meant to be a dissertation on any one topic; they are meant to stimulate ideas for developing more complete and targeted information, data, and tools on climate variability and change processes and impacts to select systems and communities.

This paper is focused on changes in the water content of the atmosphere (precipitation and water vapor) as a result of climate variability and change and some perceived and projected impacts to human health. Additionally, suggestions are made for addressing our gaps in data collection, interpretation, and application for societal benefit. Unless otherwise noted, the climate variability and change observations presented here are based on work by; Funk, C., et. al., 2008, Dettinger, M., 2011, Hidalgo, H.G., et.al, 2009, Trenberth, K.E., 2011, and Trenberth, K.E., et. al., 2013.


As the climate on Earth changes, the impacts to ecosystems, natural resources, and human health are not always well understood and current observational networks are not always designed and built with the correct targeted indicators for describing impacts and system resiliency and/or vulnerability. There are many researchers that observe impacts of climate change on the landscape for targeted ecosystems like coastal marine communities, to natural resources such as water quality and availability, and resultant human health dangers such as heat stroke and dehydration under drought conditions and changing atmospheric water content. Additionally the impacts to agricultural systems on land and food sources in the world's oceans can be severe and dramatic and our current knowledge is limited by our observational networks, human population and demographic fluctuations, and projection and forecast systems dependent on climate change datasets that may (or may not) be available and that the human health research and applications community may not be aware of.

Because of the length of time necessary to document climate change and understand and describe the driving mechanisms and processes that cause the change, scientists and decision makers rely more and more on computer model projections and forecasts that by their nature have a growing envelope of uncertainty as projection time periods increase from years to decades and centuries. In the United States, in-situ, remotely sensed, and airborne observational networks are closing at alarming rates due to budget constraints and loss of funding sources to build and maintain them. The one thing that the climate and human health research and applications communities need for better identification of and adaptation to climate change impacts, long-term targeted observational networks, are not being designed, supported, and implemented on the landscape, in the oceans, and in human health surveillance networks. The few observational networks that are being maintained are coming under budget pressures to close.

Impacts and Opportunities:

For the purpose of the discussion here, the focus is on changes in atmospheric water content (water vapor and precipitation) and the potential and observed impacts to human health. The following is a summary of the observations and important processes involved in understanding changes and patterns of precipitation and water vapor on a global scale that are currently underway with some observed or anticipated impacts on human health. The purpose of this discussion is to begin the dialogue on the much needed development of human health early warning systems and adaptation of innovative responses.

" Satellite observations over the last 40-plus years suggest that water vapor in the upper atmosphere is decreasing. On the other hand, in-situ observations over the Earth's land masses show no change and no trend during the same time period as the satellite observations. Are we becoming complacent about what might be early warning changes in the atmosphere because we don't see them at the surface of the Earth?

" Similar satellite observations over the same time period (about 1980-present depending on the satellite system) suggest a decrease in the mean monthly cloudiness over the Earth. This process would tend to add to the increase in atmospheric temperatures over this time period and would also suggest that there may be less perceptible water available to the hydrologic cycle in some areas.

" Satellite and in-situ observations suggest that there are changes in the long-term characteristics of precipitation at the Earth's surface to more intense and less frequent rain and snow fall over land masses where the human populations reside.

" With increases in evaporation as a result of higher atmospheric temperatures (on average) over the last 20-30 years and the associated shift of increasing atmospheric moisture from the subtropics into the higher latitudes, it appears that wet areas are getting wetter, and dry areas drier. For example, a) there is increased precipitation in high latitudes in the Northern Hemisphere where a majority of humans reside; (b) there are reductions in precipitation in China, Australia, the American southwest, and the small-island States in the Pacific; and (c) there is increased variability of precipitation in the equatorial regions.

" There is also a change from snow to rain, especially at the beginning and end of the cold

season globally and at higher elevations over the Earth's surface. This means that the snow pack is melting faster, is becoming diminished at the end of the spring season over time, and runoff is not available at the optimum time for the growing season in many places. This also leads to less soil moisture in the summer months with an associated risk of drought, heat waves, water shortages, wild fires, and human health impacts.

" Drinking water supplies globally are at increasing risk. Warmer atmospheric temperatures, increased evaporation of fresh surface water, rising sea level along coasts, more frequent extreme weather events, decreased snowpack in higher elevations, and earlier seasonal snowmelt all are risks to the quality and availability of fresh drinking water in more and more parts of the world with resultant impacts on human health and food sources and availability.

" The intensity and duration of drought events in some areas in Asia, Africa, Mexico, and portions of the United States have been observed to increase over the last two decades.

" With increased atmospheric temperatures and a decrease in available fresh water at the Earth's surface, the concentration of contaminants in water supplies and water vapor are on the increase. These processes affect the quality and availability of fresh water in surface reservoirs and groundwater aquifers.

" The Earth's atmosphere can hold more water vapor as air temperatures increase. However, with an associated increase in emission of contaminates through fossil fuel burning this larger amount of water vapor will be potentially contaminated and can in and of itself threaten human health.

" Water-borne disease outbreaks can be correlated with increases in air temperatures and changes in precipitation amounts and patterns. Contaminants on the increase in water and water vapor include things such as heavy metals, sediments, and black carbon (a climate forcing agent that is formed through the incomplete combustion of fossil fuels, biofuels, and biomass).

These example representations of the state of precipitation changes presented above suggest that determining the trends and drivers of precipitation variations, extreme events, and storms is critical. Recent advances in remote sensing instrumentation and the use of historical remote sensing datasets (including the Tropical Rainfall Measuring Mission (TRMM), the Global Precipitation Climatology Project (GPCP), Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN), the Chinese polar orbiting Feng-Yun-3 series satellite recently launched (Sept. 2013), and the European Space Agency's Medium Resolution Imaging Spectrometer (MERIS) on the ENVISAT satellite to name a few examples)) are facilitating the measurement of precipitation variations with relatively high spatial and temporal resolution. Global analyses of precipitation every 3 to 6 hours are available now and hourly precipitation analyses are possible. Data in these temporal and spatial scales are essential for determining the variations in, and drivers of, precipitation and water vapor variability changes on regional and sub-regional scales (river basins for example). This information can in turn be used to better understand the impacts of climate change on precipitation and water vapor changes worldwide and the impacts to human health and to essential fresh water resources. However, on the ground, in-situ networks targeted on measuring the amounts of rain fall and snow fall and the associated water content are being closed worldwide as a result of funding losses and plans for new observational networks are being postponed or eliminated.

What is missing in this discussion is the connection between observed changes in atmospheric water vapor and precipitation and the availability/utilization of this weather and climate information and data by the human health community. The use of weather and climate information to address the complexity of human health impacts of extreme events such as floods and droughts, enhanced disease transmission with increasing air temperature and changes in water vapor and precipitation, and community response (or lack thereof) is being conducted on global and regional scales with some success. Results from this work are being utilized to design and construct early warning systems for targets such as famine with the Famine Early Warning System Network (FEWS Net, see http://www.fews.net/Pages/default.aspx) and malaria or dengue fever outbreaks with SERVIR Global in Africa for example (see, https://www.servirglobal.net/default.aspx). However, few studies have been conducted on sub-regional scales such as small river basins and smaller developing countries due to a lack of observational networks, availability of weather and climate data, and a lack of health researchers to collaborate with the climate science community. The following areas of potential research and applications on climate change and human health were developed from the published works of; English et. al., 2009, IPCC, 2007, Wolf et. al., 2013, and the World Health Organization, 2012;

" A more complete understanding of the effects of water vapor and precipitation availability and their role(s) as transmission media to impact human health and agriculture

" Studies and applications focused on gaining a better understanding of the relationship between local meteorology (short term) and climate change (long term) on air and water pollution

" The role of urbanization, population growth, and changing demographics on water and air

quality as the climate changes and the associated vulnerability, or resiliency of targeted


" Improvements in the understanding and prediction of the climatology of extreme events

" Increased application of weather and climate information through geographic information systems and risk assessment tools targeting human health and food and fresh water security

" Capacity building to establish skilled applied researchers and resource managers trained in integrating climate data, information, and models with human health data, information, and models for decision support

Next Steps:

With this background, it is possible to target an ecosystem or at-risk human community that is vulnerable to water-borne contamination and changes in quality and/or availability of fresh, clean water as a result of climate variability and change; for example, a mega-city (human population of 5 million or more) such as Beijing, China, Mew York City, U.S.A., or Sao Paulo, Brazil, or a smaller developing nation such as Rwanda. In the example outlined here, a dialogue could be started between the climate science community, city or national planners, and health officials. This abbreviated example is for starting discussions and for initiating collaborative efforts and is not presented as being complete or exclusive. As a first cut during the initial discussions for forming a collaborative, integrated approach to identifying at-risk sectors in the population and the drivers of the risk(s), the following steps can be initiated,

" Teams should be formed that include engineers, scientists, health providers, economists, and decision makers.

" An inventory of existing observational networks can be made. These observational networks should be targeted for weather and climate measurements, water sources (both atmospheric and land-based), and at-risk sub-populations as well as medical infrastructure that may or may not be in place for responding to degradation of water resources, outbreaks of water-borne disease, and changes in water quality or availability.

" An inventory and cataloguing of existing weather and climate data and information.

" Model projections of climate variability and change and population and demographic changes.

" Gain knowledge of existing early warning systems and planned responses.

" Identify funding sources (local, regional, national, and international) for building resiliency and response to perturbations on water resources and populations at risk.

" Begin building capacity of trained individuals and teams in both the applied sciences and health communities and have them interact together from the start.

The challenges facing us are not insurmountable but the time is now for integrated action. In many areas of the world integrated science and applications are underway and examples should be identified and emulated.


Dettinger, M.D., 2011: Climate change, atmospheric rivers, and floods in California - A multimodel analysis of storm frequency and magnitude changes, JAWRA Journal of the American Water Resources Association 47 (3), 514-523

English P.B., Sinclair AH, Ross Z, Anderson H, Boothe V, Davis C, Ebi K, Kagey B, Malecki K, Shultz R, .Simms E., 2009, Environmental health indicators of climate change for the United States: findings from the State Environmental Health Indicator Collaborative. In Environmental Health Perspectives, Nov. v. 117 (11): pages 1673-81.

Funk, C., MD Dettinger, JC Michaelsen, JP Verdin, ME Brown, M Barlow, A Hoell: Warming of the Indian Ocean threatens eastern and southern Africa food security but could be mitigated by agricultural development, Proceedings of the National Academy of Sciences 105 (32), 11081-11086

Hidalgo, H.G., T Das, MD Dettinger, DR Cayan, DW Pierce, TP Barnett, G Bala, A, 2009, Detection and attribution of streamflow timing changes to climate in the western United States,

Journal of Climate 22 (13), 3838-3855

Intergovernmental Panel on Climate Change (IPCC), Climate change 2007. Impacts, adaptation and vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Chang, Geneva, Switzerland.

Trenberth, K. E., 2011: Changes in precipitation with climate change. Climate Research, 47, 123-138, doi:10.3354/cr00953.

Trenberth, K. E., Anthes, R. A., Belward, A., Brown, O., Haberman, E., Karl, T. R., Running, S., Ryan, B., Tanner, M., and Wielicki, B., 2012: Challenges of a sustained climate observing system. In Climate Science for Serving Society: Research, Modelling and Prediction Priorities, G. R. Asrar and J. W. Hurrell, Eds. Springer, 484 pp, 13-50.

Wolf, T., Sanchez, G., Kendrowski, V., Creswick, J., and Menne, B., 2013, Towards a European assessment of health risks of climate change, Impacts World 2013, International Conference on Climate Change Effects, Potsdam, May 27- 30.

World Health Organization, 2012, Climate Change and Health, Fact Sheet No. 266, Media Centre

Websites for reference:

Famine Early Warning Network (FEWS Net), http://www.fews.net/Pages/default.aspx

SERVIR Global, A Regional Visualization and Monitoring System, https://www.servirglobal.net/default.aspx

Tropical Rainfall Measuring Mission (TRMM), http://trmm.gsfc.nasa.gov/

Global Precipitation Climatology Project (GPCP), http://www.gewex.org/gpcp.html

Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN), http://chrs.web.uci.edu/research/satellite_precipitation/activities00.html

Feng-Yun-3, http://www.wmo-sat.info/oscar/satelliteprogrammes/view/53

Medium Resolution Imaging Spectrometer (MERIS) http://wdc.dlr.de/sensors/meris/

Randy Kieling