What is Climate Change?

From Wikipedia.org:

"Climate change is any long-term significant change in the “average weather” that a given region experiences. Average weather may include average temperature, precipitation and wind patterns. It involves changes in the variability or average state of the atmosphere over durations ranging from decades to millions of years. These changes can be caused by dynamic processes on Earth, external forces including variations in sunlight intensity, and more recently by human activities.

"Climate changes reflect variations within the Earth's atmosphere, processes in other parts of the Earth such as oceans and ice caps, and the effects of human activity. The external factors that can shape climate are often called climate forcings and include such processes as variations in solar radiation, the Earth's orbit, and greenhouse gas concentrations.

"Weather is the day-to-day state of the atmosphere, and is a chaotic non-linear dynamical system. On the other hand, climate — the average state of weather — is fairly stable and predictable. Climate includes the average temperature, amount of precipitation, days of sunlight, and other variables that might be measured at any given site. However, there are also changes within the Earth's environment that can affect the climate."

In the last fifty years, changes have been occurring in the global climate that are unprecedented in both the scope and speed at which the changes are taking place. Although there has been considerable debate as to the root causes of these changes, there is now widespread consensus within the scientific community that these changes are most likely caused by human activity, specifically the emission of so-called "greenhouse gases" by industry and transportation.

Greenhouse gases, most commonly carbon-dioxide and methane, interfere with the re-radiation of incident solar energy through the atmosphere and back into space. The thermal energy thus trapped is instead transferred to the atmosphere, raising its temperature. This mechanism, usually referred to (somewhat incorrectly) as the "greenhouse effect," is actually what gives the Earth a liveable climate. Should the bulk of the solar energy reaching the ground simply be re-radiated back into space, the Earth's climate would be not unlike that of Mars, our nearest planetary neighbour. On the other hand, the other planet nearest to Earth, the planet Venus, is an example of a runaway greenhouse effect. Its atmosphere is about 97% carbon dioxide, and - despite the fact that due to the reflectivity of its permanent high-level cloud layer, more than 60% of solar energy is reflected back into space - temperatures at the surface of Venus near the equator can be high enough to melt lead.

Since the middle of the 20th century, carbon dioxide levels in the Earth's atmosphere have undergone an unprecedented increase, and in that time the global temperature has also risen about 1 degree celsius, which is already enough to cause widespread, and in some cases, catastrophic changes to local weather patterns. For example, almost the entire continent of Australia is in the grip of a severe drought which has now lasted more than five years. About 500,000 square kilometres of sub-Saharan Africa is similarly in a drought situation, for the first time since human colonization of this area (at least 5,000 years). The region is rapidly becoming an extension of the Sahara desert.

Island groups like the Maldives and Falkland Islands are disappearing, under the onslaught of severe storms and rising sea levels. Arctic permafrost is melting; the North polar ice cap is shrinking, and the south polar ice sheet is becoming fragmented and permeable, which is having a severe impact on the stability of the Antarctic bioregion. Earthwatch Institute now says that, for the first time in human history, the number of "environmental refugees" (people fleeing regions that are no longer able to support them due to environmental changes) exceeds the number of political refugees, i.e. people fleeing regions of political instability: about 25 million environmental refugees, versus 23 million political refugees. Both of these numbers are likely to rise in the coming years, as increasing climate instability precipitates increasing political instability.

In addition, several processes are now taking place within the global ecosystem which appear to be self-sustaining and self-accelerating. The reduction in size of the polar ice cap also reduces its reflectivity, allowing more energy, previously reflected back into space, to be transferred to ocean water, raising its temperature still further. The rising ocean temperature is interfering with its ability to act as a carbon sink, allowing more carbon dioxide to persist in the atmosphere, increasing the greenhouse effect and raising temperatures still further, and so on.

Despite the uncertainty about how this warming trend will affect global weather on a long-term basis, it is becoming increasingly clear that climate change will have a significant, and very probably negative, effect on human activity over the next century, unless radical steps are undertaken to curtail or significantly alter those human activities which are most contributory.

In 2007 the IPCC (Intergovernmental Panel on Climate Change) published its Fourth Assessment Report (AR4), which discussed the physical scientific basis for an analysis of climate change, the impacts, adaptation strategies and global vulnerabilities, and mitigation options. In it, the science behind the previous AR has now been called into question. In particular, it is now apparent that feedback mechanisms in the global climate are poorly understood, but may be having a far more significant impact on the trajectory of climate change than previously thought. The AR2 and AR3 documents indicated that the effect on the north polar ice cap of continued global warming, if unaltered, could result in the complete absence of polar ice in summer by the year 2080. However, photographic evidence from space has suggested that the decrease in polar ice is progressing far more rapidly than predicted, to the point where the polar ice cap may be gone in summer as early as 2020, a full 60 years earlier than originally predicted.

The acceleration of the observed impacts from climate change may be the result of these feedback systems. As mentioned, the reduction in ice cover greatly reduces the planet's albedo, or reflectivity, allowing more solar energy to remain in the atmosphere.

The increase in arctic ambient temperatures has also resulted in the melting of some permafrost, which in turn is causing the release of large amounts of primordial methane gas, which was previously trapped within the frozen tundra. Methane is an extremely potent greenhouse gas, approximately 30 times more effective than carbon dioxide, and while methane does not persist as long in the atmosphere as CO₂, it is important to note that methane photodegrades into CO₂.

Yet another feedback mechanism results from the warming of the upper layers of the ocean in temperate and tropical regions. Close to 50% of the oxygen in the atmosphere (and thus 50% of the carbon sinking capability of the biosphere) takes place in the uppermost 6 feet of ocean waters, as the result of the respiration of near-microscopic organisms called phytoplankton. As the ocean temperature rises, the water becomes more acidic (from the absoption of carbon dioxide, creating a dilute solution of carbonic acid), which interferes with the ability of phytoplankton to maintain the calcium shell that protects them. As the phytoplankton population decreases, so does its ability to respirate carbon dioxide, thus allowing more to accumulate in the water, thus raising the acidity even more, making it still more inhospitible for the phytoplankton.

And many more mechanisms have come to light in recent years. This summary describes only the most impactful, and the most thoroughly understood. IPCC findings, based on current climate science, have indicated that in order to avoid catastrophic climate destabilization through the triggering of one or more runaway feedback systems, average CO₂ concentration in the atmosphere must not exceed 350 parts per million. Currently, the average global concentration hovers at around 390 PPM. It is obvious that in order to reach this goal, serious CO₂ emission mitigation strategies must be undertaken, and soon.

The complexities of heat propagation through the convective systems of the planet are not yet fully understood, but it is evident that as more solar energy becomes trapped within the atmosphere, the globe is not heating up uniformly. As yet, temperature increases in tropical regions are barely perceptible, less than 0.2 degrees Celsius. There are even areas of the planet where the average temperature has decreased, notably parts of the Antarctic continent, and areas off the eastern coast of the United States. However, average temperature increases in the northern arctic have been measured as high as 4-5 degrees, and it is the polar regions that are by far the most vulnerable.

Circumpolar Vortex Disruption

Paradoxically, global warming may in fact result in significantly lower mean winter temperatures here in Southern Ontario, and much snowier winters. Since the last ice age, the north polar region has been occupied by a more-or-less permanent low pressure system that blankets virtually all of the area bounded by the arctic circle. As with all low pressure systems in the northern hemisphere, it is surrounded by counterclockwise (cyclonic) air flow called the circumpolar vortex. The boundaries of the low pressure system fluctuate, and at various times of the year expand and contract, and the circumpolar air flow moves with it; this movement is responsible for much of the weather patterns that we experience in Canada. The circumpolar vortex acts to contain cold arctic air within its boundaries, allowing warmer air from the southern U.S. to flow northward into Canada, which helps to moderate our climate. The jet stream, stratospheric high velocity winds that move from west to east, generally follow the southernmost edge of the cicumpolar vortex and move weather systems along with it.

However, as the polar regions undergo significant warming, the north polar low pressure system is breaking up. Hitherto unseen regions of high pressure are appearing, and this is causing the circumpolar vortex to become unstable, and even to disappear at times. This means that arctic air no longer has a containment, and, under the influence of these new high pressure systems now appearing, can now flow unimpeded into the lower latitudes, including Southern Ontario. The result can potentially be unprecedented low temperatures in winter--perhaps coupled with heavy snowfalls as disrupted jet stream airflow brings moist air in from ocean regions--and also cooler, wet summers. The likely impacts these changes could have on local food production is as yet unknown, but may be significant.

Effects of Climate Change

The long-term impact of climate change on the global ecosystem, and on human society, is as yet a matter of "educated speculation." However, there have already been profoundly negative impacts around the world, and there is significant reason to believe that accelerating global warming will continue to have an increasingly detrimental effect. Many areas of the planet have become increasingly inhospitible to human presence, and climate change has already directly or indirectly resulted in the loss of well over ten thousand species of plants and animals, worldwide. Many biologists believe we are now in the middle of the Earth's sixth mass extinction, and that by the middle of the century, as much as 50% of the Earth's biodiversity may be lost if this trend is not reversed. This will have a profound impact on human society, particularly on our ability to produce enough food. A report by Earthwatch Institute has suggested that the effects of climate change could reduce our global food production capacity by as much as 40% by the year 2060. This is certainly not good news for human society, and as broadcaster Gwynne Dyer has speculated in his radio series Climate Wars, this could precipitate a catastrophic destabilization of the global political system, and could trigger resource wars and severe famines in many areas, including North America.

Much of the speculation around the effects of climate change have, until recently, focused on linear changes, wherein the effects on weather patterns and global climate systems is gradual and cumulative over time. This includes the most recent IPCC interim reports, and even the paper written for the U.S. Department of Agriculture by Stewart Brand's consulting firm Global Business Network reported on the likely effects of climate change on North American agriculture over a 15-year timeframe. However, the most recent paleo-climatological research, studying ice core samples taken in Greenland, have revealed the frightening possibility that catastrophic climate change, resulting from sudden releases of large quantities of methane and/or carbon dioxide, could (and has in the past) occur in as short a period as one to three years. This is certainly a disturbing finding, and although these studies are not yet complete, they do raise the alarming possibility that civilization may be blindsided by an abrupt, severe and irreversible climate event that could occur with little or no warning.

The accelerating impacts of climate change, in combination with the probable social impacts of oil depletion (see Peak Oil), may create what author Richard Heinberg (The Party's Over, Peak Everything) has described as "the perfect storm."

Climate Change and Southern Ontario

There have been several reports published recently analyzing the likely impacts of climate change on various parts of the world, region by region. In many of those reports, Southern Ontario has been listed as an area wherein climate change is expected to have little negative impact in terms of weather patterns, growing season, etc. (partly as a result of the interactions of Circumpolar Vortex disruption (above) and an overall regional warming trend, forces which would tend to cancel each other out.) However, it is important to make the points that:

1. Saying that climate change will have a relatively small impact on our climate is not the same as saying we will be unaffected. Bear in mind that much of our staple foods (wheat and other grains, for example) come from other regions that may suffer significant negative effects, which could in turn have an impact on our food security,
2. The damage to the global biosphere resulting from climate change (species extinction, changes in fresh water availability, accumulation of environmental toxins, damage to the oceans, etc.) will have a global impact, affecting all parts of the planet equally and without exception,
3. Less-impacted regions are quite likely to be inundated by climate refugees from nearby areas where the effects have been more severe, putting significant stresses on the local food system and other support infrastructures, and
4. These studies are highly speculative. The global climate is an extremely complex system, not yet thoroughly understood, and predicting its behaviour over an extended timeframe is tricky at best.

Finally... Something to Think About

The fourth mass extinction, and by far the most severe in planetary history, was the "Permian Terminal Catastrophe", which took place approximately 251 million years ago, at the boundary between the Permian and Triassic Periods. In it, almost 95% of marine organisms, and over 60% of land-based organisms disappeared, and it took the Earth over 80 million years to regain its prior level of biodiversity. It was originally believed that the Permian mass extinction was the result of a large meteor or cometary impact, but the absence of certain exotic signature chemicals in the rock strata dating from this time has cast doubt upon this theory. On the other hand, high concentrations of carbon dioxide and volcanic ash in the Permian strata has suggested that the extinction event may have resulted from a series of large volcanic eruptions in the region now known as Siberia, which pumped huge amounts of carbon dioxide into the atmosphere, triggering a runaway greenhouse effect. Based on the measured CO₂ concentrations, it has been estimated that the resulting average global temperature increases at the time may have been in the vicinity of 5.5 to 5.8 degrees Celsius.

It has been speculated that, if current trends in greenhouse gas emissions continue, we could at some point push the climate to a point of instability and into a runaway greenhouse effect--as the result of triggering the aforementioned feedback mechanisms. Should this happen, it has been estimated that average global temperature increases could reach 6 degrees Celsius by the year 2100.

"We have at most ten years, not ten years to decide upon action, but ten years to alter fundamentally the trajectory of global greenhouse gas emissions." -- James Hansen, Director Goddard Institute for Space Research, NASA - 2005