Science: How Climate Change Impacts Your Health

David Brown
Washington Post Staff Writer
Tuesday, December 18, 2007 1:00 PM

Washington Post staff writer David Brown will be online Tuesday, Dec. 18, at 1 p.m. ET to discuss the latest installment of the " In the Greenhouse" series about the science behind climate change.

Brown will be joined by Jonathan Patz, an associate professor and director of the Global Environmental Health Center for Sustainability and the Global Environment at the University of Wisconsin at Madison.

Graphic: Health Risks of Global Warming

Submit a question or comment now or during the discussion.


David Brown: Greetings chatters! Sorry we are starting a bit late; had a technical problem. But the answers are on the way. We are lucky to have with us today Jonathan Patz of the University of Wisconsin, a physician, environmental health specialist, and epidemiologist. He is a leading expert on the health effects of climate change and I appreciate his willingness to join me.

So let's go.


Washington, D.C.: Since climate change is recognized as an issue with important health implications, what is the public health community doing about it?

Jonathan Patz: HEALTH is of CENTRAL IMPORTANCE in understanding risks from climate change. the health community is engage, in fact:

1) the American Association for Public Health (APHA) has declared next year's theme of "National Public Health Week" (April 7-13, 2008) to focus on CLIMATE CHANGE ! This is actually quite a big deal, and APHA is the largest public health organization in the world.

2) the World Health Organization (WHO) has declared that their "Global Health Day" (APRIL 7) theme for 2008 is guessed it, CLIMATE CHANGE.

3) The National Association for County and City Health Officials (NACCHO) has formed a task force on climate change, and so has the Association for State and Territorial Health Officials (ASTHO).

SO... the public health community is really gearing up and mobilizing to confront climate change.


Granger, Ind.: Having been trained in the earth sciences, particularly in glaciology, I can't help but think "Chicken Little" here. From what I learned, historically, global temperatures rise and decline and are inevitable, normal cyclic occurrences. The proof abounds from geologic remains. I guess it's good to prepare but we're talking geologic time periods not tomorrow. Why sound the apocalypse horns?

Jonathan Patz: I am not a climatologist, however, collaborate with many of the best in the world on the UN IPCC. I would simply refer you to the IPCC Web site WWW.IPCC.CH

this site is easily accessible with easy to read summaries for policy makers as well as technical summaries and a synthesis report.

The climatologist are VERY concerned by the RATE OF WARMING, and for many many reasons now are able to state "with 90%" confidence" that the warming especially occurring over the past 50 years is do to human greenhouse gas pollution... and NOT simply natural climate cycle. But please do go to the IPCC summary reports. The climatologists are really concerned, and with long half-life of greenhouse gases in atmosphere (70-100 yrs), they are worried that if we don't reduce emissions soon, it will be too late to stop potential for accelerated warming.


Mount St. Joseph High School: Good afternoon;

Don't more people die worldwide from the cold as opposed to the heat? Wouldn't that mean global warming is a good thing for mortality rates globally?

Jonathan Patz: During the year more people do die in the winter season than summer. However, it is not necessarily due to cold temperatures. While still not fully known, it is thought that deaths from influenza virus may cause a spike in winter mortality ... and so far, flu virus does not depend so much on temperature. That is, warmer winters do not mean less flu.

In studies looking at both cold and hot temperature-related mortality, in the United States the "hot-slope" (deaths per degree increase of hot temperatures) is much steeper that "cold slope" (deaths for degree decrease at cold temperatures). These relationships change across cities, but for a majority of cities, people are more sensitive to hot temperatures, than to cold.


Rockville, Md.: Really, I see a very one sided argument that ignores all the benefits of warmer climate. What is the point of this agiprop? I don't doubt that we are getting warmer, but I see warmer as good with some aggravations and chages in where we live. On the other hand, another ice age could kill most of the population. Who benefits from such one sidded presentations? When I read pieces like this I really think we have an "unorganized conspiracy" that never plans together.

Often I see most of the political candidates saying "Yes, we will fix the warming problems" then go into their pet project list to fix the world. That makes them look (1) aware and (2) thoughtful. I go along with (2).

David Brown: The story was meant to be non-judgemental as to whether global warming or global cooling is good or bad in some cosmic sense. The chief question is: is it happening? and the answer appears to be Yes. (The role of human agency is in more dispute, although there is lots of evidence that human activity is contributing to climate change). The next question is: what will it do? That is what the story tried to address. There will certainly be winners. Harvests in Canada, Russia and other places are likely to be more bountiful. But the net effect is believed to be detrimental---a net effect reached with a lot of projection, estimation and averaging.


Lafayette, Ind.: In Monday's article you mentioned that changes in the climate "will tend to harm health rather than promote it" meaning that there will be some health benefits and some detriments. Your article then proceeds to only list the detriments. In order to provide a more objective story, please explain what and where will be the health benefits?

Jonathan Patz: Yes, as always there will be winners and losers. It's possible that the SE may become too hot for tick-borne Rocky Mountain Spotted fever transmission. Also places like the former Soviet Union will have longer growing season for crops. Also, I do think in some places, there should be fewer deaths from cold temperature (though analysis we are conducting shows that extremely cold days do not drop nearly as much as extremely hot days increase in the upper midwest)

However from the past 3 IPCC reports, Human Health chapters, the message has been consistent that, "on balance, the impacts with be adverse."

David Brown: I answered that in a previous question, but to reiterate, there will be some benefits to warmer average temperatures. However, the net effects are expected to be detrimental (although this all involves modelling and projection, so the uncertainty is great). It is also noteworthy that the places where the effects are expected to be the most detrimental (such as sub-Saharan Africa) are places that may have the least resiliency in handling its effects and difficulties in instituting adaptive changes in advance.


My Desk: Forecasting climate out 50 to 100 years contains huge uncertainties. As long as we have cases like this past weekend (where Friday morning they were still forecasting snow/ice for Sat and Sun, but we got none of it), I think we must view long range projects with a grain of salt. I know one is "climate" and one is "weather," but ... seems at the end of the day I don't see much difference ... I'm not trying to be a skeptic, but ...

Jonathan Patz: Again, I refer you to the climatologists and the IPCC Web site (

What climatologists tell me is that it is FAR more predictable to be correct about mid and long-term trends (e.g. over decades) than it is to predict next weeks weather.

This may not seem logical, but please go speak with a climatologist; you'll hear a similar answer repeatedly.


Emeryville, Calif.: How will the more extreme cold and hot temperatures affect mortality in the U.S.?

Jonathan Patz: please see my answers to questions 2 & 4


Bethesda, Md.: I have a professional and academic interest in infectious disease ecology and I've been doing a fair bit of research into the impacts of climate change on infectious disease patterns. My understanding is that disease prevalence is most heavily determined on the local level (i.e. land use, water quality, wildlife), but that climate shifts will impact larger scale geographic ranges. How can scientists best measure and separate the discrete impacts of climate change as opposed to these other factors?

Jonathan Patz: Yes, definitely most infectious diseases are affected by MANY factors, and indeed the local environment is extremely important. I basically agree with you, and in fact, in many tropical locations, local deforestation can affect both habitat AND local climate more acutely than will climate change.

As you say, it's the broad ranging exposure at the regional and global level thru which global warming can have adverse effects across many diseases and many locales. But as you point out, climate change is not the only key factor (and often not the most critical in short run) - so, climate change risk should definitely not be viewed in isolation from other environmental public health factors

Jonathan Patz: Just to add some examples to your question about measuring discrete effects, different locations will carry varying risks. For example, extremes of the hydrologic cycle (more floods and droughts) would tend to increase the risk of Valley Fever (fungal pneumonia) in the desert southwest.

Whereas the midwest is expected to have more stagnant air masses, leading to worsening smog ozone "Red Alert Days", as well as more frequent heat waves. Also, our own model projections are showing more floods in midwest, which would threaten drinking and recreational waters (remember the cryptosporidiosis outbreak in Milwaukee, 1993? In our analysis, that event was preceded by the heaviest month of rainfall in the previous 50 years climate record).


Bethesda, Md.: The thinking reflected in many of the comments here is why, in the end, this all amounts to nothing but a nice little academic discussion. It doesn't matter that global climate change is actually happening, that humans are causing it, and that there might still be a chance to do something about it. Sadly, the political will is not there, and will not be there until it's far too late, and we will not do squat about it.

Jonathan Patz: I understand your concern, and it is a very challenging task. HOWEVER, I actually see a lot of political will rapidly emerging. For example:

1) more than 600 mayors have now signed onto a Climate Protection Initiative to reduce emissions across their cities;

2) Many govenors are establishing task forces and committees to advise them on how to reach huge cuts in greenhouse gases (certainly California, but I can also say that my own govenor of Wisconsin, Governor Doyle, has form such a special committee, and he recently convened a meeting of midwest states and a Canadian Province to begin a carbon trading market

3) the supreme court ruling on CO2 as a pollutant to be officially regulated.

So, I am actually OPTIMISTIC !


Washington, D.C.: Hello, I'm a researcher at the Worldwatch Institute. I recently wrote about natural disaster risk in cities, and one of the stats that most surprised me is that persistent small-scale disasters (localized flooding, landslides, etc--the kind that never make the news) cause as much--or more--suffering and damage than large disasters like hurricanes or tsunamis. The same must hold true for public health and climate change--that many of the health effects will (at least initially) be small, localized outbreaks that are hard to pinpoint to climate change, even if they are directly related. What methods are being used to get around this challenge? Thanks, Zoe

David Brown: This is an interesting question---which causes more suffering, big world-news disasters, or local ones that don't get widely reported? I don't have the competence to provide an answer. But there is a very interesting website at the University of Louvain, in Belgium,

that keeps a record of disasters, down to local floods in which only a few people are killed. The answer can probably be found there, with some research.

What is clear is that there are local vulnerabilities. For example, there may be two coastal cities that are each at risk of flooding from torrential rains or storm surges. If one has an old water system with many leaks it will be at greater risk of intrusion of ground water and possible contamination than a city with a newer, more water-tight distribution network. Similarly, if a city or region tends to have power plants, water plants, schools, bus fleets, etc. in the flood plain then it will be more vulnerable to effects of a storm surge than a place where those things are on higher ground. A few cities are starting to inventory their possible vulnerability to such events, but generally there hasn't been a lot of advanced planning for the effects of climate change.


San Diego: Please comment on the likely decrease in solar UVB irradiance (a key source of vitamin D) due to the increasing effects of the brown cloud. There is already a vitamin D deficiency epidemic in many countries leading to greater mortality from many cancers. It is likely that this will increase--something could be done now, however to help with this.

Jonathan Patz: This is a pretty tough question and concerns particulates (blocking sunlight). Not sure I have the answer, but general it's important that people understand that the UVB issue linked to the ozone hole (stratospheric ozone depletion) is a different problem from global warming (though some climatologists say there are some interactions).

But key point is that even if we solve the ozone hole by banning CFCs we have not solved the global warming problem.

More info on both these issues can be found at:


Rockville, Md. : By the by, I have worked in science libraries for over 30 years and have an earned a PhD.

Jonathan Patz: Thanks. Please have your library check out:


Baltimore, Md.: Why has there been no reporting of the letter written by a large group of scientists saying that the large amounts of money being spent on climate change would be better off spent on more pressing problems?

Jonathan Patz: Interesting question. Let me ask you a question. If you were an emergency room doctor and had to chose whether or not you should treat the patient bleeding out on the floor from a knife wound ...VERSUS the patient that walks in with high blood pressure?

Of course, you 1st treat the bleeding person. but high blood pressure (a silent killer) kills more people.

So you the end you must treat BOTH, the acute AND long term health threats. The budget pie has more than just 2 pieces (that is, why sacrifice future health for current emergencies). how about cutting non health budget items instead.

David Brown: I am not aware of the letter you are speaking of and would be interested in learning more about it if you can send me a copy at


David Brown: I think we're out of time. One minor clarification; the university in Belgium that is the repository on data on disasters is Universite Catholique de Louvain - Brussels. Since 1988 it has been the WHO Collaborating Center for Research on the Epidemiology of Disasters.

I appreciate Dr. Patz being on here to answer most of the questions. He is with the Department of Population Health Sciences at the University of Wisconsin and the Center for Sustainability and the Global Environment (SAGE) whose Web site is:

He has another website that may be of interest to educators and the public

Thanks again for your questions and time.

David Brown: Please join future "In the Greenhouse" chats.


Editor's Note: moderators retain editorial control over Discussions and choose the most relevant questions for guests and hosts; guests and hosts can decline to answer questions. is not responsible for any content posted by third parties.

View all comments that have been posted about this article.

© 2007 Washingtonpost.Newsweek Interactive