This lecture is dedicated
to health and climate change.
We shall see what are the constraints of climate on
human societies that do indeed determined human health.
In the past and even more recently,
we see that climate can have direct and indirect effects on human societies.
Direct effects through, for example,
heat and cold waves or drought that can affect agriculture, for example.
The direct effects such as sea level rise or the change
of areas that are prone to vector-borne and waterborne diseases.
Indeed, if we look at the controls of climate on
various factors that determine human well-being and survival,
we see that there are very strong links between climate and water resources,
food resources, health and shelter.
Any change in one or more of these parameters affected by changing climates will,
of course, directly or indirectly affect humans.
If we look at some of the projections of climate change by the end of the century,
we see that temperatures will rise almost everywhere on the globe.
The increases will be stronger in
the northern latitudes than in the tropical and equatorial latitudes, simply because,
the conditions of Arctic sea ice and what takes place in
the polar latitudes will be changing much more rapidly
than in the already warm and moist tropical regions.
When we think about climate change,
we think foremost about temperature change but of course,
many other factors will be also
changing as temperatures increase over the course of the century,
in particular, precipitation which is, of course,
a major driver of water resources.
We see that most models are suggesting that precipitation will
decrease in regions where precipitation is already
scarce today such as the tropical zones,
the Sub-Saharan Africa, for example.
But middle and high latitudes may actually see an increase in precipitation.
There is, of course, a seasonal difference with summertime in
the Northern Hemisphere experiencing
much more frequent drought conditions as we experienced in Europe,
for example, during the 2003 heatwave.
Indeed, drought, dry conditions,
explain to a large extent the intensity and
the duration of that very severe heatwave from 2003.
If we look at what could be some of the direct health impacts of a changing climate.
Well, of course, there are many.
I'll just take this one example which is drawn
from a paper that was published by Keatinge et al.,
in the British Medical Journal,
which shows a fairly interesting graph between mortality and temperatures.
One sees that there is a optimum for different regions of the world where cold conditions
can exacerbate mortality on the one hand and
warm or hot conditions would also increase mortality on the other hand.
So, if you're in a cold climate that is warming,
you could actually have a gain in terms of lowering mortality rates,
simply because you're moving towards the optimum.
Whereas, if you're already in a climate that is today optimal,
for example, in Switzerland,
and you move to a much warmer climate,
than you can see that on this graph you will move into higher risk zone for mortality.
So, this is typically one of the direct possible effects of a warming climate.
However, the indirect effects are probably much more important, in the sense that,
by impacting upon water resources, food,
shelter, there will be many side effects that would determine human health.
In this graph of cereal yields,
by the end of the century,
one sees that many parts of the world will actually see a decrease in
agricultural production of basic foodstuffs especially in the tropical countries,
those that are already on the demographic and economic stress today.
So, a lowering of food security would have an indirect effect on human health,
so fragilize possibly already fragile populations.
Looking at the impacts of infrastructure.
Higher rates of flooding as we saw, for example,
during the Katrina hurricane in New Orleans or more
recently in the Australian floods of 2010.
This graph just shows us the statistics from major insurance,
reinsurance company that shows us that
whether it's in terms of the number of victims, the total cost,
or the insurance cost,
climate impacts are by far those that create the most damage even in today's climate.
So, you can imagine that the combined effects of a changing
more variable possibly more damaging climate
with increasing populations in zones at risk would,
of course, impact upon the damage to
infrastructure especially in the developing countries.
So, again, the factor that could fragilize already fragile populations.
Then, we have, of course,
the direct and indirect effects of water quality and
vector-borne diseases influenced by a warming climate.
This map of Africa shows us the possible rates of
incidents or additional incidence of malaria with just one degree of warming.
One sees that there is a very distinct geographic zone
where the increase of malaria might be possible.
This is simply linked to the altitude of the terrain in
which malaria might actually enter in the future.
In other words, with a one degree warming conditions
that today are not favorable for the advent of
the anopheles mosquito that propagates malaria would in
tomorrow's world enable the vector to invade these regions.
In terms of waterborne diseases or warmer climate will, of course,
change the conditions that are favorable for a number of
vector-borne diseases as you see on this table here, where you have, of course,
the big water-related diseases such as schistosomiasis, African sleeping sickness,
leishmaniasis and so on,
which would, of course,
see an increase in the number of people potentially affected by these diseases,
as the conditions for the vectors within
stagnant or flowing water bodies would actually change because of warmer waters.
But when we talk about the health impacts of a changing climate,
we need to take into account many other factors.
On this graph, you see that poverty and demographics are amongst
the major determining factors upon which
climate will be an additional exacerbating factor.
So, populations at risk are not only populations
facing a changing climate but those that do not have necessary,
unnecessarily access to health care,
to education, to technology,
that would actually help them to alleviate the risk associated with
a changing climate and its impacts on human health.
The World Health Organization has in the past 10 or 15 years actually
brought out a number of documents on climate change and its impacts upon health.
In its latest document published in 2009,
has a set of recommendations that include advocacy to raise
awareness to the fact that climate change can be an exacerbating factor for human health,
partnerships to coordinate with UN agencies to ensure
that health is properly represented in the climate change arena.
Of course, we need more science and evidence
that climate change and the manner in which climate change will impact upon human health.
So, we need actually education programs to raise awareness,
to make sure that populations that are
more remote or economically fragile parts of the world,
gain access to this knowledge and therefore take
the appropriate measures to alleviate the risk
associated with a changing climate on human health.
Thank you very much for your attention.
Rafael Ruiz De CastañedaInstitute of Global Health - Faculty of Medicine
Antoine FlahaultProfessor of Public Health and Director of the Institute of Global Health (Faculty of Medicine, University of Geneva) and co-Director of Centre Virchow-Villermé (Université Paris Descartes)
