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Climate change and health: an overview

The worst effects of climate change on health and other aspects of our lives may still be avoidable

Dr Philip Michael, Honorary Assistant Secretary, Irish Doctors Environmental Association (IDEA), Dublin

August 3, 2015

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  • Climate change is a reality and is happening now. It will affect every aspect of our lives over the next few decades and way into the future.1,3 It is not just an environmental issue but has major economic, political, social, cultural, educational, security and of course, health implications. As regards the latter, in 2009, after a year long commission held jointly between The Lancet and University College London, involving many disciplines, the opening sentence of the resulting executive summary is: “climate change is the biggest global health threat of the 21st century”.4

    Climate change is inevitable, but its worst effects may still be avoidable, mitigation (significant reduction in greenhouse gas [GHG] emissions) is required in conjunction with adaptation to help us cope with the inexorable upcoming changes.

    At present, global emissions of GHGs continue to increase, largely due to the ‘catch-up’ effect of developing countries. Because there is a lag period between the release of GHGs and the temperature rise, and because the gases persist in the atmosphere for a prolonged time, the current burden of gases will continue to cause warming for many centuries. If we continue in a ‘business as usual’ scenario it will inevitably lead to further increasing global temperatures which are already set to top the so-called ‘safe’ limit of 2°C by 2050.2 This will destabilise the planet’s ecosystems with potentially devastating results for humanity.

    However, by working together pro-actively, health professionals can – instead of facing the ‘biggest global threat to health’ – turn it into ‘one of the most significant health opportunities’.5,58 It is vital that we act immediately as there is increasing evidence that incremental adaptation may not be sufficient to avoid intolerable risks. Transformative change may now be required.3

    The International Panel on Climate Change (IPCC)

    In 1988 the IPCC (International Panel on Climate Change) was formed jointly by UNEP (United Nations Environmental Program) and the WMO (World Meteorological Organisation) due to scientists’ increasing concerns about evidence emerging that climate was changing, which was thought to be at least partly due to the release of CO2 from fossil fuel combustion.6 It is an intergovernmental organisation representing 195 UN member states and it has produced a number of reports known as ‘Assessment Reports’ (AR), beginning in 1990 (FAR – First Assessment Report) and repeated approximately every five to six years. 

    The most recent is AR5, which was released in 2013/14. The reports are always in three sections, produced by three working groups (WG) with a summary for policy makers (governments, etc) plus a ‘Synthesis Report’ for each part. 

    WG1 deals with the physical basis of the evidence; WG2 deals with the impacts, adaptation and vulnerability; WG3 deals with mitigation. An unprecedented level of scientific collaboration underpins the various IPCC reports. They involve thousands of scientists across many disciplines and their consensus reports are based on scrutinising thousands of published, peer-reviewed papers. These are in turn further reviewed by multitudes of other experts and government officials on a line-by-line basis. 

    Reports are informational/advisory rather than prescriptive, and are worded very carefully to avoid ambiguity or confusion. 

    The science of climate change

    The basic science whereby certain gases in the atmosphere have a warming effect is well understood and has been recognised since the 19th century. Approximately one-third of the sun’s incoming radiation (short-wave, ultraviolet and visible light) is reflected back into space by the earth’s atmosphere and the rest is absorbed by land and the oceans. They in turn give out long-wave radiation (infrared) which is absorbed by atmospheric gases – mainly CO2 (carbon dioxide), methane (CH4), ozone, water vapour (H2O) and nitrous oxide – the so called ‘green house gases’ (GHGs).6

    This effect is an essential prerequisite for a mild, stable global temperature, such as has permitted the evolution of the extensive biodiversity in the world today. Unfortunately, the recent increase in concentration of these gases in the atmosphere, due mainly to human activity (burning fossil fuels/deforestation/agricultural practices/production of cement) in the past 150 years, has resulted in an increase in the average global surface temperature.2  

    There are two important points to note about CO2, the main GHG:

    • One is that the average global surface temperature is proportional to the atmospheric CO2 concentration – the higher the concentration the higher the temperature. This has risen in the past century and a half from approximately 280ppm (parts per million) to 400ppm last year, an increase of about 40%, and it is still increasing.2,7
    • The second point is that, once released, CO2 remains in the atmosphere for a very long period (thousands of years). Therefore the CO2 we are releasing now will remain as a ‘climate forcing agent’ for millennia. In Ireland, the last 30-year period has been the warmest for the past 800 years (climate is officially measured in 30-year periods).8 Crucially, the rate of warming has been greater than anything that has occurred in the past 2.5 million years.

    Climate forcing and feedback

    Forcing refers to cosmic or earth-based changes that alter the earth’s temperature and thereby destabilise climate. Feedback may be either positive – causing increased warming, or negative – causing decreased warming. Factors include:

    • Changes in the earth’s orbit and axis tilt which leads to shifts in geographical and seasonal sunlight over 20,000 to 400,000 years, eg. the various ice ages
    • Albedo (reflectivity). Increased reflectivity is cooling (negative feedback) but warming means more ice and snow melt, therefore less reflectivity causing increased heat absorption causing more melting = positive feedback
    • CO2 increases: a) natural – warming soils and oceans release more CO2 and other GHGs which in turn causes increased greenhouse effect = positive feedback; b) anthropogenic – burning fossil fuels, farming practices, destruction of forests
    • Aerosols, eg. black carbon (volcanoes, coal burning), can be deposited on snow/ice reducing reflectivity = positive feedback. Also, by blocking incoming radiation they may have a cooling (‘dimming’) effect = negative feedback
    • Water vapour is a very important positive forcing agent.  The warmer the atmosphere/ocean, the greater the evaporation, the higher the water vapour concentration.2

    Tipping points

    The IPCC has identified certain ‘tipping points’ which could result in uncontrollable, runaway climate change due to feedback mechanisms (see below). In other words, instead of a gradual (but historically very rapid) warming, certain factors (combinations of identified risks) could precipitate an abrupt, severe rise in temperature with catastrophic consequences for all global ecosystems. These include:

    • Permafrost melt: the release of vast quantities of methane. Also from the seabed, methane hydrates in a warming ocean
    • Arctic sea ice loss: loss of reflective snow and ice causing increased heat absorption – the albedo effect
    • Greenland ice sheet melt: increased heat absorption and elevation of sea level
    • Boreal and Amazon forest die back: release of CO2 and loss of carbon ‘sink’
    • Instability of the west Antarctic ice sheet – additional sea level rise
    • El Nino Southern Oscillation (ENSO) change in amplitude or frequency: increase in extreme weather events.2

    “An Armageddon is approaching at the beginning of the third millennium. But it is not the cosmic war and fiery collapse of mankind foretold in sacred scripture; it is the wreckage of the planet by an exuberantly plentiful and ingenious humanity.” Professor EO Wilson, Harvard University (‘The father of Ecology’)

    The 2ºC limit

    In 2007 the AR4 defined 2°C (3.6°F) as the maximum temperature rise compatible with a reasonable chance of maintaining stable ecosystems and human social systems.9 This 2°C limit was confirmed politically in Copenhagen (COP15) in 2009 (The Copenhagen Accord).22

    Many experts believe that even this level of warming is technically dangerous and there is also a growing consensus that without immediate, drastic cuts in carbon emissions this limit will be exceeded.21 The effects will primarily be physical and environmental (ecological), with knock-on effects on all human systems, including healthcare systems.3

    The bottom line for global warming is the cumulative emissions of GHGs (UNEP Febuary 2014). In order to limit warming to less than 2°C it is essential that the total emissions must stay below 800GtCe (gigatonnes Carbon Equivalent). The total already emitted between 1870 and 2011 is 550GtCe, so sustained reduction is essential.21,29

    Effects of global warming

    We are thus now committed to a warming world, but how much? How quickly? And with what effects? The IPCC has attempted to answer these questions in their five reports over the past 25 years. Worryingly, as the evidence mounts and the sophistication of the climate modelling improves, the predictions and warnings have become increasingly severe.

    Sea levels

    Melting ice and snow will contribute to sea level rise along with thermal expansion of water due to heating. The Greenland ice cap melt will be the major source of excess water in the short-term, along with mountain glaciers.3 There has recently been strong evidence that the west Antarctic ice sheet that heretofore had been thought to be a low risk for melting, is in fact becoming unstable.21,23 This would add an extra 3.4m to global sea level rise in addition to the most recent estimate of the order of 1m by the year 2100. These estimates assume in part a linear relationship between warming and sea level rise but it has been agreed that in a business-as-usual scenario (BAU) of CO2 emission there could be a non-linear response of multi-metre sea level rise this century.

    Ocean acidification

    The oceans are becoming more acidic due to the absorption of excess CO2 causing the formation of carbonic acid. This is already affecting the shells (calcium carbonate) of various marine species, including coral reefs. They (oceans) are estimated to absorb about one-third of excess carbon and the pH has gone from 8.2 to 8.1 (25% increase in acidity) and is predicted to fall to pH 7.8.23

    Biodiversity loss

    Biodiversity is essential for a healthy environment. In turn this is essential for human health. There are many ongoing chronic threats to biodiversity including overpopulation; overharvesting of resources; invasive species; land use changes (agricultural practices); overuse of artificial fertilisers (nitrogen); chemical contamination of the biosphere; deforestation; extremely high electromagnetic radiation levels, GM plants and the direct effects of excess CO2 on plant growth and development. Most of these factors are contributing to a global reduction or extinction of species ongoing over many decades. 

    There is evidence that the global ecosystem as a whole is approaching a ‘state shift’ – a tipping point – on a planetary scale, as a result of human impacts that could be abrupt and irreversible.60 Climate change is likened by many  health professionals to an acute illness on a planetary scale which, particularly over the past 30 years, is compounding the chronic pre-existing illnesses as above.4 In AR4 (2007) the IPCC estimated that if there is global warming above 1.6°C, 9-31% of species will be committed to extinction. If average temperatures rise to 2.9°C, 21-52% of species will become extinct.1 Many scientists are now saying that we are in the midst of the sixth great extinction.

    Extreme weather events

    A warmer atmosphere holds more moisture and also increases evaporation in dryer areas leading to worldwide flooding events and droughts in certain areas. Modelling predicts that as CO2 increases, such extremes – including storms, hurricanes, etc – will become more severe and more frequent in most parts of the world.21,25

    Shifting climate zones

    There is wide natural variability in annual temperature changes, but in the past 30 years there is evidence that isotherms (lines of a given average temperature) have moved pole-wards at a typical rate of 100km per decade and also upwards in elevation.26 This is far in excess of any possible natural rate of change. These large changes are disruptive for the biosphere and have the potential to cause difficulties for all species in affected areas, though humans tend to be more adaptable.

    Health and social wellbeing impacts

    Direct impacts on health and social wellbeing include extreme weather events such as heat waves; floods and droughts; storms, hurricanes, typhoons, fires; all causing deaths, illness, injuries and infrastructural damage.

    There are also indirect impacts through ecological disruption (natural systems), and a changing in infectious disease patterns; food and water borne diseases; and air pollution causing increased mortality and morbidity.

    Indirect mediated through human social systems

    These include social disruption; forced immigration; conflict; undernutrition and starvation; breakdown of social structures, food production/distribution and infrastructure damage; and security considerations relating to all the above.3

    Most research on health effects of climate change relate to effects caused by warming to the so called ‘safe’ limit of less than 2°C global average. More recent research quoted by the IPCC indicates that there are doubts about whether this limit can be maintained.3 The IPCC report states that “it can be assumed that the increase in many important climate-related health impacts will be greater than simple linear increments”.3

    “Climate change threatens the basic elements of life for people around the world – access to water, food production, health and the use of land and the environment.”

    Executive Summary Item Review – Economics of Climate Change, UK Government released October 2006 (The Sterne Report)

    Food security

    The impacts of climate change on agriculture/horticulture has the potential to cause the most severe and widespread impacts on health globally. Although warming temperatures and higher CO2 concentrations may initially promote plant growth, other factors such as water stress and higher temperature extremes can quickly damage crops. It is predicted that for each degree of warming, yields of corn in the US and Africa and wheat in India will drop by 5-15%.3 If temperatures rise by 5°C, most regions of the world would experience yield losses and global grain prices could double (US National Research Council 2012).

    The present CO2 atmospheric concentration as mentioned is 400ppm and that is increasing at a rate of 2ppm/year.2 There is considerable scientific opinion that it is insufficient to reduce emissions, that it is necessary to reduce the atmospheric concentration to 350ppm.20

    To date CO2 reduction in emissions has proved politically impossible. Noted US journalist author and climate researcher Bill McKibben commented “In a rational world policymakers would have heeded scientists when they first sounded the alarm 25 years ago. But in this world, reason, having won the argument, has so far lost the fight. The fossil fuel industry, by virtue of being perhaps the richest enterprise in human history, has been able to delay effective action, almost to the point where it is too late”.29

    Since the 1970s, global warming has caused over 140,000 excess deaths per annum, costing US$ 2.4 billion according to WHO estimates. Weather-related disasters result in 60,000 deaths per annum. Malnutrition and undernutrition currently cause 3.5 million deaths/year; diarrhoeal diseases cause 2.2 million deaths/year; all these are predicted to increase with rising temperatures with women and children, the poor and the old, mainly in developing countries, bearing the brunt according to the WHO.30

    This is an abridged version of an article on ideaireland.org

    References

    © Medmedia Publications/Forum, Journal of the ICGP 2015