1. What is global warming? Our planet is
getting warmer due to greater concentrations of greenhouse gases in the atmosphere.
Significant greenhouse gases include
carbon dioxide (CO
2),
methane,
nitrous oxide, and
fluorinated gases. Their presence in the atmosphere
has the effect of trapping the sun’s heat near the earth rather than letting it dissipate into space.
Ice core samples provide data on atmospheric CO
2 levels going back 800,000 years; these data and other evidence suggest that levels, while fluctuating slowly, were relatively stable until the time of the Industrial Revolution. The escalation of fossil fuel combustion since that time has resulted in a
significant increase in the concentration of CO2 and other greenhouse gases in the atmosphere. (
Here is a movie showing CO
2levels from 800,000 years ago to the present.)
Deforestation alters the carbon cycle as well by removing the CO
2“sinks” which allow the biosphere to reabsorb CO
2. Instead of stability, we are now in a period of warming, with manifold effects on regional climates and habitats, at a rate that is too fast for most species to adapt.
2. Are we sure? Yes.
The vast majority of climate scientists agree that global warming is taking place and that it is caused by human activity. These are scientifically established facts, not a matter of opinion or political belief. As with any large, complex system, it is difficult to make exact predictions about the consequences of global warming on specific regions, habitats, and populations. However, there are sound scientific and historical reasons for predicting that global warming will have a significant negative impact on human populations and all the planet’s inhabitants, and it is essential that we investigate and prepare for these consequences. This is not a scare tactic; it is the only responsible course of action.
3. Which human activities are we talking about here? Using fossil fuels releases greenhouse gases. This occurs during the
mining,
refining, and
combustion of fossil fuels (as well as during the
mining of uranium for nuclear reactors). All practices which currently depend on fossil fuels (
electricity production,
heating,
transportation,
manufacturing,
agriculture, etc.) contribute to global warming. In addition, large-scale agricultural practices contribute to the release of
methane and
nitrous oxide, as well as
deforestation, which is another significant cause of global warming. The only way to address global warming is to transform or replace these practices.
4. What are the large-scale effects of global warming, and how do they translate into regional effects? The areas of the earth where warming is taking place fastest are the
polar caps and the
oceans. As polar ice caps shrink,
sea levels rise,
changing coastlines and causing some
small land masses to disappear altogether. An increase in ocean temperatures can cause
changes in currents,
changes in wind patterns, and
more powerful storm systems. Changes in weather patterns and regional climates can lead to changes in
cloud cover,
precipitation,
mountain snowpack, and
availability of fresh water. While the average temperature of the earth continues to rise, some regions may experience
colder winters due to greater weather volatility. In addition, infusion of CO
2 into the oceans causes an
increase in acidity. Changes in marine and terrestrial habitats will result in changes in plant and animal populations, with a
domino effect up the food chain, as well as changes in landscape and
erosion processes.
8. What will be the impact on species survival and biodiversity? Rising ocean temperatures are already causing a
dramatic die-off of phytoplankton, microscopic organisms that are at the base of the marine food chain. Changes in polar habitats are already affecting the many species that inhabit them, such as
polar bears, penguins, whales, and seals. Species extinction rates over the next century are expected to be about
10 times greater than recent global averages, due to changes in habitat, seasonal onset, migratory patterns, saltwater infusion into freshwater systems, and other effects of climate change due to global warming. The consensus is that global warming will have a
significant negative impact on biodiversity.
9. What will be the impact on national security? In May 2014, a US Military Advisory Board released
a report detailing the many ways that climate change may fuel regional and international conflict, including economic instability, food insecurity, water scarcity, population migrations, and an increase in catastrophic weather events. In March 2014, the Pentagon’s
Quadrennial Defense Review included the following passage on page 8:
Climate change may exacerbate water scarcity and lead to sharp increases in food costs. The pressures caused by climate change will influence resource competition while placing additional burdens on economies, societies, and governance institutions around the world. These effects are threat multipliers that will aggravate stressors abroad such as poverty, environmental degradation, political instability, and social tensions – conditions that can enable terrorist activity and other forms of violence.
10. Can we stop global warming? No, not in the short term. But we can slow the rate of global warming, prevent some of the worst scenarios, prepare for and adapt to change, and, over time, reverse some of the effects of global warming. Our biggest and most urgent tasks are to curtail the release of greenhouse gases into the atmosphere, by transitioning from fossil fuels to
sources of energy with no climate impact (solar, wind, hydroelectric, geothermal, biomass), and to
halt deforestation. We need to direct considerable resources toward these tasks and overcome significant obstacles. But the consequences of inaction or inadequate action will probably be dire or catastrophic for much of the earth’s population.
