Global Climate Change and the Dominican Republic
Michael C. MacCracken
Climate Institute, Washington DC
3 June 2006
Abstract
Ocean temperatures are rising; powerful hurricanes seem to be occurring more frequently; coral reefs in many regions are suffering; sea level is becoming higher; and news report describe changes in the climate that are occurring around the world, from the melting back of Arctic sea ice to the deathly hot summer of 2003 in Europe. International scientific assessments undertaken by the Intergovernmental Panel on Climate Change (IPCC) indicate that all of these changes, and many more, are symptomatic of the increasing pace of global climate change, often referred to simply as "global warming." This paper provides an overview of how human activities are changing atmospheric composition, how these changes have the potential to and are changing the climate, and how continuing reliance on coal, oil, and natural gas is projected to alter the climate during the 21st century. While the UN Framework Convention on Climate Change was adopted in 1992 in an effort to stabilize the climate, such large reductions in the use of coal are unlikely by the end of the century, meaning we and the environment will, in the meantime, have to adapt to the changing climatic conditions.
Human Activities are Changing Atmospheric Composition
When coal, oil, and natural gas are burned to power society's activities, the carbon that has been chemically bound up in these substances, often for tens to hundreds of millions of years, reacts with atmospheric oxygen, creating carbon dioxide (CO2) that is released into the atmosphere. Present emissions from these fuels, which are together referred to as fossil fuels because the fuels result from the fossilized remains of long dead plants and animals, are adding about 7 billion tonnes of carbon (GtC) per year to the atmosphere. The cutting down of forests and depleting of fertile soils, if not balanced by regrowth of plants and root matter, is also resulting in emission of CO2 to the atmosphere; net global emissions are estimated to be about 1-2 GtC per year. For reference, the 8-9 GtC added to the atmosphere each year due to these activities is about equivalent to the total amount of carbon taken up to green the Northern Hemisphere each spring and summer.
With the world population approaching 7 billion people, each year each person in the world is responsible, on average, for about 1 tonne of carbon (tC) from fossil fuel combustion and about 0.2 tC from deforestation and unsustainable agriculture. However, actual usage varies quite significantly depending on standard-of-living and the level of industrial activity. Where there are few cars, air-conditioned buildings, or industry, as is the case in many developing nations, per capita emission of fossil-fuel carbon is less; however, in these nations, per capita emissions from biomass-derived carbon can be relatively high because wood is serving as an important fuel.
By contrast, in industrialized countries characterized by widespread air and road transport systems, home and business ownership, and industry, per capita usage can be several times higher than the global average. Variations among countries and regions arise due to a number of factors, including the prevailing climate, the availability of hydroelectric and other renewable sources of energy, the amount of industrial and mining activities, the exporting and importing of energy and products that require energy, and the degree of state efforts to improve the energy efficiency of buildings, appliances, and transportation. While the regrowth of forests and enhanced uptake of CO2 by plants as the CO2 concentration rises do lead to the sequestering of carbon, this uptake mainly makes up for past elimination of vegetation cover and only marginally offsets long-term fossil-fuel emissions.
With each nation depending on others for food, energy, locally produced and imported products, and the like, the energy required to support societies occurs around the world-we are locked into this problem together. As both world population and the average standard-of-living continue to rise, continuing reliance on fossil fuels to power global economic development is going to lead to much greater global emissions in the future. If, for example, the world population grows by 50% by the end of the century, and on average each of the 10 billion people relies on fossil fuels for about half the amount of energy used by Europeans (or about a third of that used by North Americans), annual per capita emissions will be about 2 tonnes of fossil fuel carbon; multiplying these terms together, total emissions will be about 20 billion tonnes of carbon per year, or about 3 times the current level.
Looking at the world from space, one might wonder how anything humans do could lead to significant change. But the atmosphere is very thin and CO2 is a pretty stable molecule. Combining observations from the global sampling network established in 1957 and from measurement from earlier times using "old" air trapped in bubbles in ice cores, the records indicate that human activities have increased the atmospheric CO2 concentration by over 30%, from about 0.028% to about 0.038% of the Earth's atmosphere, since the start of the Industrial Revolution about 250 years ago. Multiplying the change in concentration by the volume of the atmosphere indicates that the atmospheric CO2 burden has increased from about 550 GtC to about 750 GtC over this period. This increase in burden is about half as large as the estimate of total emissions of carbon from fossil-fuel use and from deforestation over the past few centuries.
But why is there an increase at all given that both global vegetation and the oceans can take up large amounts of CO2 each year? In particular, photosynthesis enables land plants to convert CO2 into plant matter, removing about 120 GtC from the atmosphere each year, and the mixing of air with ocean water enables the oceans to take up and dissolve into ocean waters about 90 GtC per year. Were this a one-way transfer, the human addition of about 8-9 GtC per year would seem to have a small influence. However, rather than the biosphere and oceans accumulating all this carbon each year, they give virtually all of it back through other processes. In particular, for the oceans, this occurs as a result of dissolution in warm ocean waters, and for plants, as a result of their own respiration and decay and also the conversion of plant material back to CO2 by humans and other animals. A person eating is a good analogue: as long as a person eats and expels the same amount, their weight stays the same, but increase the intake by a doughnut (or dulce de coco) each day, and over time, the weight adds up, especially if, as is happening in the real world, we are doing the equivalent of eating more and more doughnuts.
Increasing the Concentration of CO2 and Other Greenhouse Gases Exerts a Warming Influence
Were the Sun the only source of energy for the surface of the Earth, planetary temperatures would average near freezing, being high for sunlit conditions and very low at night. Fortunately, in addition to all the nitrogen (N2) and oxygen (O2), the Earth's atmosphere includes a number of gases that are made up of three or more atoms rather than just two. These additional gases, including water vapor (H2O), carbon dioxide (CO2), ozone (O3), methane (CH4) and others, are called greenhouse gases because they are largely transparent to incoming solar radiation, but are able to absorb a large fraction of the upward directed heat radiation emitted by the Earth's surface to balance the surface absorption of sunlight. The upward-bound energy that these gases absorb warms the atmosphere, and this causes the atmosphere, like any body that is warmed, to itself radiate its heat away. What is important is that the greenhouse gases radiate heat both upwards and downwards, with the upward radiation subject to further absorption before being lost to space. The downward directed heat radiation adds to the effect of the solar energy and causes the Earth's surface to warm. With the Earth now a bit warmer, it emits more radiation upwards, more is absorbed by the greenhouse gases, and then more is radiated back down to the surface, causing further warming. In addition, the warmer the Earth's surface, the more water is evaporated into the atmosphere, and so the more effective is the set of greenhouse gases in warming the surface. By the time everything reaches equilibrium, and averaging to account for both day and night, the global average of the heat e
nergy radiated from the atmosphere to the surface (which is basically recycled sunlight) provides roughly twice as much energy to warm the surface as the incoming sunlight. Thus, just as the roof of a greenhouse limits loss of energy from a greenhouse, the greenhouse gases trap heat to warm the Earth.
Comparison of the climates of Venus and Mars with that of the Earth make clear that the more greenhouse gases a planet has, the higher will be its surface temperatures. Records derived from ice cores tracing Earth's history back now for about 650,000 years give the same indication. There is thus no question that increasing the atmospheric CO2 concentration (and human activities are also increasing the atmospheric concentration of CH4 and other greenhouse gases) will tend to cause the Earth to warm.
The Earth's Climate is Warming, in Good Agreement with Changes in Atmospheric Composition
Although it has taken more than a century, warming of nearly 1ºC resulting from human activities has now become evident in the record of global average temperature. Temperature measurements have been taken on ship cruises and at a global network of stations for about the past 150 years, and when the records are analyzed to see if change has been occurring, virtually all locations in the world show unusual and relatively strong warming, especially over the last 50 years. Prior to that time, there are hints of change, but most of the fluctuations appear to result from the cooling that is induced for a few years following major volcanic eruptions, warming and cooling from small variations in solar intensity and the El Niño and La Niña events in the equatorial Pacific Ocean, and from the cooling effects of the sulfate-laden haze (i.e., SO4 particles) that created as a result of emission of sulfur dioxide (SO2) as a byproduct of coal combustion. Careful analyses that look for the characteristic pattern of changes of each factor (i.e., the "fingerprint" of each influence) make clear that the warming influence of human activities now dominates the changes that were occurring as a result of natural variations in sunlight and volcanic eruptions.
A wide variety of other indicators confirm that the world is warming. Temperatures below the land and ocean surfaces are both increasing, and the ocean warming is expanding ocean waters and contributing to sea level rise. Snow cover, permafrost, and sea ice are melting. Mountain glaciers in the tropics and high latitudes are melting at unprecedented rates, and their melt water is also being added to the oceans. Plant and animal species are, where they can, shifting their ranges, and where they can't, like coral, undergoing much more stressful conditions. Taken together, it is clear that humans have become now the largest factor affecting the climate, and our influence is growing.
Climate Change Will Intensify Over the 21st Century
Combustion of coal, oil, and natural gas currently provides roughly 80% of the world's energy-it is critical to the survival of the world's people and there is no way that the world can simply stop using fossil fuels. Because carbon makes up such a large fraction of these fuels, there is no easy way to scrub it out as is now done for SO2 in order to limit acid precipitation, visibility reductions, and ecological damage. Even with major commitments by all the world's nations, it will take many decades to convert over to other sources of energy. Over this time there would be considerable emissions of CO2-and if the world delays in getting started on this conversion, there will be that much greater emissions, and therefore warming.
The IPCC's periodic assessments of the state of scientific understanding have assembled the projections for the 21st century generated by climate models developed by research groups from around the world. Climate models-that is, theoretically based constructs of the world on a computer-are the only quantitative tool available for making 100-year projections. Other approaches have been considered, but the world is too complex to reconstruct as a laboratory model and Earth history does not provide any examples of the extent and rate of change in atmospheric composition from which close analogues can be drawn. Scientists can and do test the abilities of their models to represent climatic variations in the distant and recent past and over long and short periods, but the complexity of the Earth system is such that there still remains quite a range in the estimates of how typical weather conditions (which are then averaged together to generate an estimate of changes in climatic conditions) will differ from the present for a range of different projections of how global population, economic development and energy technologies will change.
Assembling all of the model results, the IPCC's Third Assessment Report in 2001 projected that the increase in average temperature around the world would range from about 2 to 4.5ºC, with changes being larger than average in mid to high, over land, in winter rather than in summer, and at night rather than during the day. The reasons for this include the extra warming influence resulting from snow meltback in high latitudes (with less snow, less solar radiation is reflected), the larger heat capacity of the ocean than the land, and the potential for evaporation (where moisture is present) to limit the temperature increase. While the smaller temperature increase in low latitudes sounds appealing, the accompanying increase in atmospheric water vapor concentration would make the small temperature increase feel relatively uncomfortable (that is, the discomfort index is projected to rise by more than the temperature increase).
The increase in the atmospheric water vapor concentration is also projected to lead to more intense rainfall events, and, indeed, records in many countries indicate that such changes are already occurring. Trends are also beginning to indicate that hurricanes and typhoons are becoming more intense-that is, the central pressure is dropping, the peak wind speeds are increasing, and, to power these changes, more energy is being derived from the condensation of the water vapor that is present as a result of the warmer sea surface temperatures, and so rainfall is becoming more intense. That the observed changes are larger and are occurring more rapidly than the models have projected is currently the focus of intensive scientific research.
Global Climate Change Will Matter to Those in the Dominican Republic
What these changes will mean for the Dominican Republic will depend on both what is happening globally and what happens locally. The rise in the CO2 concentration itself will tend to acidify the oceans, creating a problem for all tropical regions because it will become more difficult for ocean organisms to generate shells and coral. Global climate change will affect the world economy, the production and purchasing capabilities of trading partners, the extent and spread of vector-borne and infectious diseases, and the vitality of natural resources that the Dominican Republic shares with the world (e.g., migrating birds and whales). In addition, global climate change will affect the large-scale circulations of the atmosphere and oceans (so the strength and phasing of the intertropical convergence zone), the characteristics of hurricanes, and the rate of melting of mountain glaciers and polar ice sheets, which, along with warming of the oceans, will accelerate the rate of rise of global sea level to roughly 0.3 to 0.5 meters per century, or higher if the Greenland Ice Sheet starts to rapidly deteriorate.
It will take local experts to translate the projected changes in the average behavior of the global atmosphere into likely changes in local weather. Doing this will require detailed consideration of local geographic conditions and coupling to the seasonal variations in the region's weather and oceanic conditions, including translating estimates of the rise in global sea level to its local manifestation. Using local estimates of changes in, for example, the duration, intensity, and shifting of precipitation regimes, the likely impacts on water resources, agricultural production, tourism, and other activities can be evaluated, determining along the way the potential for locally adapting and adjusting in order to limit negative consequences and take advantage of new opportunities, all in the context of how one's competitors are being affected and responding. As a general guide, what everyone will need to be doing is accounting for ongoing climate change in all of their long-term planning, considering not only the most likely projections, but accounting also for the increase or decrease in risk that is possible if conditions instead turn out to be as much worse or better as is acknowledged in the statements of scientific uncertainties. Through interactive efforts between the local scientific community and those who make a living in ways coupled to the weather and the climate, information about the potential changes can be distilled into the type of useful information that should be able to help in informed and foresightful decision-making.
Many Decades Will be Required to Stabilize the Climate
Recognizing the importance of acting to limit climate change, the UN Framework Convention on Climate Change was negotiated at the Rio Earth Summit in 1992 and soon adopted by virtually all of the world's nations. It set as its objective "stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system." The Kyoto Protocol, which went into effect in 2005, is a small first step in this direction. To actually stabilize the global climate will require much more, ultimately cutting emissions of CO2 by roughly 80% below current levels while at the same time supplying enough energy to provide for a rising standard-of-living for the growing world population. Even after such a dramatic transformation of the global energy system, climate change will continue for several decades and sea level rise will continue for many centuries, making it absolutely essential that, in the interest of the situation that will be faced by our grandchildren and their grandchildren, the world not only start now to take really serious steps toward limiting emissions, but also fully incorporate consideration of the coming changes in climate and sea level into public and private decision-making about future infrastructure, production, and education.
Resources for Additional Information
1. Reports of the IPCC are accessible on the Web at http://www.ipcc.ch/pub/pub.htm
2. The Climate Institute Web site includes a compilation of many reports on the likely impacts of climate change (see http://www.climate.org/CI/index.shtml).
3. The Web site of the Global Energy Sustainable Islands Initiative provides information on steps to take to help limit the pace of climate change (see http://www.gseii.org/).
May 15, 2007
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