Page 374 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

338 part II The Water, Weather, and Climate Systems
on Climate Change (UNFCCC) that set specific targets to reduce emissions of greenhouse gases. Canada signed the Kyoto Protocol in 1997 but became the only country to withdraw, in 2012. In 2009 Canada signed the Copenha- gen Accord, which calls for it to reduce greenhouse gas emissions by 17% below 2005 levels by 2020, but that tar- get is not expected to be achieved. Since the time of these initial climate warnings and policy actions, climate change science has advanced, and the issue of human- caused climate change has moved from one of scientific and public debate to one of general scientific agreement.
Taking a Position on Climate Change
Despite the consensus among scientists, considerable con- troversy still surrounds the topic among the public at large. The disagreement takes two forms: first, disagreement about whether climate change is occurring, and second, disagreement about whether its cause is anthropogenic. The fuel for the continuing “debate” on this topic appears to come, at least partly, from media coverage that at times is biased, alarmist, or factually incorrect. The bias often reflects the influence of special-interest groups, and some errors come from simple misinterpretation of the facts. Media misinformation often comes from corporate inter- ests whose financial gains are at stake if climate change solutions are imposed. Another source of misinformation is the growing number of blogs and other social media that often present results not yet evaluated by other scientists. Such information is sometimes inaccurate and may be sen- sationalized. The bottom line is that having an informed position on climate change requires an understanding of Earth’s physical laws and system operations, and an aware- ness of the scientific evidence and ongoing research.
In Chapter 1, we discussed the scientific process, which encourages peer evaluation, criticism, and cau- tious skepticism through the scientific method. Many would argue that skepticism concerning climate change is simply part of this process. However, climate scien- tists have generally reached consensus: The case for anthropogenic climate change has become more con- vincing as scientists gather new data and complete more research, and as we witness actual events in the environ- ment. However, as new information becomes available, scientists will constantly need to reevaluate evidence and formulate new hypotheses.
When considering the facts behind climate change, several key questions can help guide you to an informed position based on a scientific approach:
• Does increasing atmospheric carbon dioxide in the atmosphere cause warming temperatures?
Yes. Scientists know that CO2 acts as a greenhouse gas and that increased concentrations produce warm- ing in the lower atmosphere. Scientists have under- stood the physical processes related to atmospheric CO2 for almost 100 years, well before the effects of global warming became apparent to the scientific community or to the public in general.
• Does the rise of global temperatures cause global cli- mate change?
Yes. Global warming is an unusually rapid increase in Earth’s average surface temperature. Scientists know, based on physical laws and empirical evidence, that global warming affects overall climate; for exam- ple, it changes precipitation patterns, causes ice melt, lengthens growing seasons, impacts ecosystems, and leads to rising sea level and coastal erosion.
• Have human activities increased the amount of greenhouse gases in the atmosphere?
Yes. As discussed earlier, scientists use radioactive carbon isotopes to measure the amount of atmospheric CO2 that originates from fossil-fuel burning and other human activities. They now know that human sources account for a large and growing percentage of these CO2 concentrations.
• If climate change on Earth has occurred in the past, then why are the present conditions problematic?
Carbon dioxide concentrations are today rising more quickly than is seen throughout most of the long-term climate record. This rate of change puts Earth systems in uncharted territory for assessing im- pacts, at a time when Earth’s human population ex- ceeds 7.3 billion.
• Can scientists definitively attribute the changes we are seeing in climate (including extreme events and weather anomalies) to anthropogenic causes alone?
One issue needing further study is the effect of mul- tiyear oscillations in global circulation patterns (such as ENSO) on short-term changes in climate. Scientists do not yet know the extent to which global warming is driving changes in the intensity of ENSO and other os- cillations, or whether the changes result in part from natural variability.
Action now Means “no Regrets”
Given this scientific knowledge base, taking action on climate change must focus on lowering atmospheric CO2. As emphasized in the 2007 and 2013–2014 IPCC re- ports and many others, opportunities to reduce carbon dioxide emissions are available and have benefits that far offset their costs. These are sometimes called “no re- grets” opportunities, because societies have little to lose and much to gain by employing these strategies. For ex- ample, the benefits from reducing greenhouse gas emis- sions include improved air quality, with related benefits to human health, reduced oil import costs and related oil tanker spills, and an increase in renewable and sus- tainable energy development, with related business op- portunities. These benefits exist separately from the fact that all of them will decrease the rate of CO2 accumula- tion in the atmosphere, and thus slow climate change.
A report by the government of Canada in 2011 pro- jected net savings of $1.7 billion if its target specified by the Copenhagen Accord, 17% reduction in green- house gas emissions below 2005 levels by 2020, were met. A similar study for the United States in relation to