We’ve all experienced the effects of climate change over the past decade. However, it’s not straightforward for climatologists to make the connection between a warming climate and specific weather events, and most are justifiably reluctant to ascribe any specific event to climate change. In this respect, the best measures of climate change are those that we can detect over several decades, such as the temperature changes shown in Figure 19.2.2, or the sea-level rise shown in Figure 19.3.1. As already stated, sea level has risen approximately 20 cm since 1750, and that rise is attributed to both warming (and therefore expanding) seawater and melting glaciers and other land-based snow and ice (melting of sea ice does not contribute directly to sea-level rise as it is already floating in the ocean).
Projections for sea-level rise to the end of this century vary widely. This is in large part because we do not know which of the above climate change scenarios (Figure 19.2.4) we will most closely follow, but many are in the range from 0.5 m to 2.0 m. One of the problems in predicting sea-level rise is that we do not have a strong understanding of how large ice sheets, such as Greenland and Antarctica, will respond to future warming. Another issue is that the oceans don’t respond immediately to warming. For example, with the current amount of warming, we are already committed to a future sea-level rise of between 1.3 m and 1.9 m, even if we could stop climate change today. This is because it takes decades to centuries for the existing warming of the atmosphere to be transmitted to depth within the oceans and to exert its full impact on large glaciers. Most of that committed rise would take place over the next century, but some would be delayed longer. And for every decade that the current rates of climate change continue, that number increases by another 0.3 m. In other words, if we don’t make changes quickly, by the end of this century we’ll be locked into 3 m of future sea-level rise.
In a 2008 report, the Organisation for Economic Co-operation and Development (OECD) estimated that by 2070 approximately 150 million people living in coastal areas could be at risk of flooding due to the combined effects of sea-level rise, increased storm intensity, and land subsidence. The assets at risk (buildings, roads, bridges, ports, etc.) are in the order of $35 trillion ($35,000,000,000,000). Countries with the greatest exposure of population to flooding are China, India, Bangladesh, Vietnam, U.S.A., Japan, and Thailand. Some of the major cities at risk include Shanghai, Guangzhou, Mumbai, Kolkata, Dhaka, Ho Chi Minh City, Tokyo, Miami, and New York.
One of the other risks for coastal populations, besides sea-level rise, is that climate warming is also associated with an increase in the intensity of tropical storms (e.g., hurricanes or typhoons), which almost always bring serious flooding from intense rain and storm surges. Some recent examples are New Orleans in 2005 with Hurricane Katrina, and New Jersey and New York in 2012 with Hurricane Sandy (Figure 19.3.2).
Exercise 19.4 Rainfall and ENSO
This graph shows the monthly precipitation data for Penticton from 1950 to 2005 along with the ENSO (El Niño Southern Oscillation) index values. High ENSO index values correspond to strong El Niño events, such as 1983 and 1998. Describe the relationship between ENSO and precipitation in B.C.’s southern interior. It’s not necessarily a consistent relationship.
By SE, using precipitation data from Environment Canada and ENSO data from http://www.esrl.noaa.gov/psd/enso/mei/table.html
The geographical ranges of diseases and pests, especially those caused or transmitted by insects, have been shown to extend toward temperate regions because of climate change. West Nile virus and Lyme disease are two examples that already directly affect Canadians, while dengue fever could be an issue in the future. Canadians are also indirectly affected by the increase in populations of pests such as the mountain pine beetle (Figure 19.3.6).
Exercise 19.5 How Can You Reduce Your Impact on the Climate?
If you look back to Figure 19.2.3 and the related text, you can easily see what aspects of our way of life are the most responsible for climate change. Think about how you could make changes to your own lifestyle to reduce your impact on the climate. It may depend on where you live, and the degree to which fossil fuels are used to generate the electricity that you use, but it’s most likely to include how, how far, how fast, and how frequently you move around.
If you hold the opinion that there isn’t much point in making changes to your lifestyle because others won’t or because your contribution is only a tiny fraction of the problem, bear in mind that all of us have the opportunity to set an example that others can follow. And remember the words of the American anthropologist Margaret Mead: “Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has.”