Fruit and Nut
|Climate Change and Global Warming|
Introduction to climate change
Climate Change is the term used to describe long term changes in weather patterns. Such changes have occured throughout the period that life has existed on this planet. It is well documented that long-term cycles influenced by irregularities in the earth's orbit and rotation cause distinctive warm and cold phases of thousands of years in duration. The last intense cold spell, usually referred to as The Ice Age (though there were many other Ice Ages prior to this one) , ended around twelve thousand years ago. Since then, there have been many smaller climate fluctuations, many of them still big enough to have major impacts on human civilisation. A warm period of approximately three centuries during the Middle Ages assisted the development of agriculture across many Northern European countries. The colder spell that followed - often referred to as the Little Ice Age - reined in agricultural expansion and saw tillage replaced by livestock farming (and sometimes orchards) in many places. More recently still, roughly since the end of the nineteenth century, global temperatures have begun to rise. Since the mid1980s, the rate of temperature increase has steepened significantly, to around 0.2°C per decade. Although this does not sound like much, data from ice cores, tree rings and other sources suggests that such a rapid rise in global temperature has not occured at any point in the last ten thousand years, and possibly not for far longer. If this increase continues, as climate science predicts - the earth will soon be warmer than at any time for thousands of years.
This time is different
While historical changes in climate have been almost entirely due to natural cycles, the changes that have occured during the latter part of the industrial era - particularly those of the last three decades - are different. Science has shown that the recent increases in global temperature are anthropogenic, in other words directly linked to human activities. The temperature increases are caused by rising levels of greenhouse gases in the atmosphere. These gases are called greenhouse gases because they cause more of the sun's heat to be trapped in the atmosphere, in the same manner as glass traps heat inside a greenhouse. And these additional greenhouse gases are the result of human activities such as cutting down forests, livestock farming and the of burning fossil fuels (oil, gas and coal). The principal greenhouse gas is carbon dioxide and is released into the atmosphere mainly by burning fossil fuels (oil, gas and coal). Methane - released by livestock and also by disturbance of wet soils - is the second most significant greenhouse gas.
Although some people - particularly those with vested interests in the fossil fuel industry or with lifestyles that might be impacted upon by any attempt to rein in fossil fuel use - have denied that recent global warming is anything to do with human actvities, the fact is that the overwhelming majority of the world's climate science community believe global warming is caused by human activities and their findings, published by the body known as the Intergovernmental Panel on Climate Change (IPCC) have been endorsed by the governments of every single member state of the United Nations.
Owing to the on-going effect of greenhouse gases already in the atmosphere, even if all the anthropogenic emissions were somehow halted tomorrow, global temperatures would continue to rise for a number of decades. Unfortunately however, the rate of global greenhouse gas emissions continues to rise, and with almost every country in the world increasing its emissions year on year, no change in this trend is likely (or even possible) in the near future. Meanwhile, global temperatures are set to continue rising for many decades, and possibly into the next century.
General Outlook (Europe)
The official EU position:
"Annual average land temperatures over Europe [over the remainder of this century] are projected to continue increasing by more than the global average temperature. The largest temperature increases are projected over eastern and northern Europe in winter, and over southern Europe in summer. Annual precipitation is generally projected to increase in northern Europe and to decrease in southern Europe, thereby enhancing the differences between currently wet regions and currently dry regions. The intensity and frequency of extreme weather events is also projected to increase in many regions, and sea-level rise is projected to accelerate significantly."
Source: www.eea.europa.eu/soer-2015/europe/climate-change-impacts-and-adaptation (see link below)
Interpretation: the scenario RCP 4.5 is predicated on significant reductions in anthropogenic greenhouse gas emissions. The RCP 8.5 scenario is predicated upon existing policies on global warming, and the continuation of current trends in energy use.
Projected changes in precipitation for Scenario RCP 8.5. The combination of reduced summer precipitation in tandem with increased evapotranspiration arising from higher temperatures will have massive implications for food production.
Precipitation Maps North America (Projected changes in precipitation 1961-1980 to 2080-2099)
Source: United States Environmental Protection Agency
The most notable impact is likely to be on California, the leading producer of many crops in the United States. California produces over 99 percent of the United States' almond, pistashio, walnut and rice crops, 97 percent of the plums and kiwis, 95 percent of the garlic, 60 percent of all carrots grown in the United States, and is the leading US producer of many other fruits and vegetables, as well as the being the largest dairy producer. In addition to supplying the rest of the United States, California also exports food to many other countries. The principal markets are Canada, the EU, Japan, China and Mexico. Excluding wine, the main agricultural exports are nuts, rice, dairy products and fruit.
California is already experiencing severe water shortages, as are the neighbouring states of Arizona, New Mexico, Nevada and Utah. All of these states can expect significantly reduced precipitation as the effects of global warming bite.
Although hailed as a success, the most notable feature of Paris was the absence of any binding reduction targets or dates. Even if all the pledges made by the participating nations are actually implemented (a highly unlikely scenario given the political considerations for the governments involved) the world is still on course for a 2.7-3.0°C rise on pre-industrial temperatures. Unfortunately, the1.5°C aspirational target mentioned in the Paris agreement is now almost beyond reach.
The text of the Paris agreement can be read here
Global Warming Implications for Future Food Security
All credible climate-change scenarios point to higher temperatures and altered rates of precipitation. Many key food producing regions (for example the countries of Southern Europe and Western Asia, the southwestern states of the United States, Mexico, Egypt, the Indian subcontinent, and Australia) will suffer declining water availability, mostly directly from reduced precipitation but in some cases also indirectly from non-replenishment of subterranean aquifers and from diminishing seasonal glacial melt in adjacent mountain areas (as the glaciers retreat or disappear). Crop losses will vary widely, from relatively insignificant to potentially catastrophic.
Although some of these losses may be offset by increased food production in regions where global warming improves prospects for agriculture (for example parts of Canada, Scandinavia and Russia), these hypothetical increases in output are contingent on the successful alignment of many competing cultural, ideological, economic, environmental and logistical factors (particularly in the case of Russia). In any event, in a world threatened by diminishing food supplies, the price of staple foods on world markets is likely to go off the scale.
Both Ireland and the UK, with their high dependency on imported food (and in Ireland’s case, high dependency on imported energy too) will be vulnerable to any major disruption to global food supply chains. In both cases, the only remedy will be to increase production of crops intended for local consumption.
Climate Change Risk Assessment
In 2015, the UK Foreign Office commissioned a report into the long term risks of global warming. The report was produced by the Centre for Science and Policy at the University of Cambridge. Some extracts from the executive summary are copied below:
Current policies and plans for major countries and regions are, in aggregate, consistent with a medium to high emissions pathway, with emissions continuing to increase over the next few decades.
The technological challenges to achieving a low emissions pathway are substantial, and are not being adequately addressed at present. Without an acceleration of innovation in energy technology and energy systems – including wind and solar with storage, nuclear, biofuel, petroleum-free passenger transport, carbon storage, and large-scale energy efficiency – the likelihood of following a pathway in which emissions fall rapidly and approach zero by late in the century is very low.
High emissions pathways in which emissions continue to increase throughout the century cannot be ruled out, given the potential for extraction of large new coal reserves, as well as oil shale and methane hydrates.
The climate responds to cumulative emissions, so any pathway that does not bring emissions close to zero will result in risk continually increasing over time.
For any emissions pathway, a wide range of global temperature increases is possible. On all but the lowest emissions pathways, a rise of more than 2°C is likely in the latter half of this century. On a medium-high emissions pathway (RCP61), a rise of more than 4°C appears to be as likely as not by 2150. On the highest emissions pathway (RCP8.5), a rise of 7°C is a very low probability at the end of this century, but appears to become more likely than not during the course of the 22nd century. A rise of more than 10°C over the next few centuries cannot be ruled out.
Humans have limited tolerance for heat stress. In the current climate, safe climatic conditions for work are already exceeded frequently for short periods in hot countries, and heat waves already cause fatalities. In future, climatic conditions could exceed potentially lethal limits of heat stress even for individuals resting in the shade. The probability of exposed individuals experiencing such conditions in a given year starts to become significant for a global temperature rise of around 5°C, and could exceed 50% for a global temperature rise of around 7°C, in hot areas such as northern India, southeastern China, and southeastern USA.
Crops have limited tolerance for high temperatures. When critical thresholds are exceeded, yields may be drastically reduced. The probability of crossing such thresholds in a given year, for studied examples of maize in the Midwestern US and rice in southern China, appears to rise from near zero at present, to become increasingly significant with global temperature rise of more than 2°C, and in the worst cases to reach somewhere in the region of 25% (maize) and 75% (rice) respectively with global temperature rise of around 4-5°C.Biophysical limits on the extent to which such tolerance thresholds can be raised may be an important constraint on adaptation. This is one reason why high degrees of climate change could pose very large risks to global food security.
With 1m of global sea level rise, the probability of what is now a ‘100-year flood event’ becomes about 40 times more likely in Shanghai, 200 times more likely in New York, and 1000 times more likely in Kolkata. Defences can be upgraded to maintain the probability of a flood at a constant level, but this will be expensive, and the losses from flooding will still increase, as the floods that do occur will have greater depth. Thresholds of adaptation beyond which ‘retreat’ from the sea may become more feasible than further increases in flood protection are not well defined, but the most significant limits may be sociopolitical rather than economic or technological.
Climate models suggest that global sea level rise is unlikely to exceed 1m this century, and that a plausible worst-case scenario could result in an increase of several metres by the end of the 22nd century. However, due to inertia in the climate system, with a sustained global temperature rise of 2°C the global sea level may be committed to rise by some 10-15m as ice-sheets gradually melt, but whether this will take hundreds of years or thousands of years is deeply uncertain.
Many elements of the climate system are capable of abrupt or irreversible change. Changes to monsoons or to ocean circulation patterns, die-back of tropical forests, and the release of carbon from permafrost or sub-sea methane hydrates could all cause large-scale disruption of the climate. The probabilities of such changes are not well known, but are they expected to increase as the global temperature rises.
The report warns of the possibility of climate change risk being underestimated:
Scientists are conservative about drawing incorrect conclusions—so much so that they would rather draw no conclusion than an incorrect one. Consequently, they have developed standard practices and cultural norms to protect the scientific knowledge pool from being contaminated by falsehoods. For example, scientists typically apply statistical tests that estimate the probability that a predicted outcome may have happened purely by chance rather than because of a hypothesized cause. If the probability of the random outcome is greater than five percent, standard practice is to reject the hypothesis. Ironically, this rigor often results in the rejection of a correct hypothesis because there was only a small chance—potentially less than 6 percent—that the hypothesis was indeed a random outcome.12 Such scenarios involve two types of uncertainty, or ‘error’ in statistical terminology. First is the possibility that the hypothesized cause is accepted, but is actually wrong. This condition is commonly called a ‘false-positive;’ statisticians call it a ‘type I error.’ Conversely, there is the possibility that the hypothesis is rejected, but is actually correct. This situation presents a false-negative, or ‘type II error.’ Scientists are relatively tolerant of false-negatives...
...Consistent with their aversion to type I error and tolerance of type II error, climate scientists have often erred toward underestimating risk when faced with deep uncertainty.
The full report can be accessed here
Arctic Sea Ice Melt
The basic premise of the convention is that Arctic sea ice melt represents a non-reversible tipping point in global climate change. Prior to the era of global warming, the part of the sea ice would melt each summer and reform again over the winter months. The month with the least ice is normally September. After this new ice begins to form. But in recent years the minimum area of summer sea ice has declined dramatically, from around 7 million km² at the start of the 1980s to only 3.39 million km² in 2012. This decline has been much more severe than even the most extreme of the IPCC climate change scenarios (which suggested the ice would only shrink to these minimums sometime between 2025 and 2050).
More information on historical Arctic sea ice area is here
If this general trend continues, which seems very likely, the central part of the Arctic ocean is likely to be ice free for the first time in tens or hundreds of thousands of years, sometime within the next ten years. The event itself (of an Arctic ocean free of ice) is not likely to represent the tipping point, but more a signal that the earth has already passed it. We say this because already, many significant changes are happening at the Arctic. The loss of sea ice is causing the albedo (relfectivity) of the Arctic ocean to change. Sea ice reflects upwards of 50 percent of incoming solar radiation back into space, while open water reflects only 5-10 percent. The additional ocean areas that are ice free in summmer are now warming rapidly which in turn is warming the polar atmosphere, leading to increased ice cap melt over Greenland as well as the warming of the permafrost regions of northern latitudes. Permafrost melt is releasing more carbon dioxide and methane (the principal greenhouse gases) into the atmosphere, adding to the potential for further global warming. And so the cycle continues.
But more frightening still is the spectre of methane hydrate melt. The methane hydrates are deposits of methane in frozen sediments situated under the seabed of the East Siberian Shelf. Normally the sea is cold enough to maintain these sediments in a frozen state (the freezing point of sea water is -2C). But now the sea is warming, the deposits of methane are being released. All told, the deposits hold hundreds of times more methane than is currently in the atmosphere. Methane is a very powerful greenhouse gas, with 28-84 times the global warming potential of carbon dioxide.
More information on Arctic climate change
For more information on what is happening at the Arctic as a result of sea ice melt, see this short interview with Dr Natalia Shakhova, one of the world's leading authorities on polar methane hydrate emissions. Dr Shakhova has spent the last decade carrying out research at the East Siberian Shelf, where vast quantities of ancient methane are trapped within and below frozen sediments. These sediments are now melting, releasing the methane into the atmosphere. If only 1 percent of the methane escapes, it will double global atmospheric methane levels. Here Dr Shakhova discusses the inevitability of this event, and the likely timescale.
Global Implications of Arctic Climate Change
Interview with Peter Wadhams, Arctic climate scientist and author of A Farewell to Ice: here
The Operating System of Global Civilisation is Seriously Flawed
This documentary featuring many of the world's leading climate scientists explains the Arctic crisis and its likely implications: here
UK report warns of food security risks from global warming
A new report published in the UK warns of food security risks from global warming. One of the priorities flagged by the report is to 'assess the nature and scale of changing land suitability and its impacts, including by conducting further research into more resilient crop varieties, tree species, livestock regimes and farming systems'.
The report goes on to warn of the 'deterioration of high-grade agricultural land: due to increasing soil aridity, reduced water availability for irrigation, the depletion of soil organic matter, and sea level rise...the proportion of agricultural land in England and Wales classed as ‘best and most versatile’ (Grades 1, 2 and 3a) is projected to decline from 38% to 9% by the 2050s under a high climate change scenario. Current crop production in areas of eastern England and Scotland could become unviable due to the combination of drying soils and lack of dependable water supplies for use on farms.'
Similar impacts on food production are likely to occur in Ireland too. To download the report, click here (4MB)
Further information on food security:
Food security in Ireland: Climate change impacts, adaptation and mitigation within the livestock sector and options for improved food security outcomes, Andi Wilson 2016 (full paper here)