Predicted Impacts

Scientists' best estimates of impacts include:

• rising sea levels (estimates are increasing, but several feet are the lower bounds), which could wipe out billions of dollars worth of coastal development, critical coastal ecosystems, and force the relocation of millions of people inland;
• a decline in soil moisture (as surface temperature increases, there is greater evaporation), which could radically alter the conditions under which we grow our food--though we produce enough food to feed the world currently, its distribution is skewed and currently over a billion people go to bed hungry. And .... because water vapor is a greenhouse gas, it poses other problems for the climate. There is less local moisture, potentially changing rainfall patterns, creating a self-reinforcing cyucle of less moisture and higher temperatures.
• more severe storms, unpredictable climate change. Tornadoes, hurricanes, cyclones and other tropical storms, wildfires, and just extreme rainfall leading to more flooding, as well as less snow and more rain (which would be a problem for flooding in the Pacific Northwest).
• Increased drought--there may be just as much rainfall, but its distribution will change, more may come in the form of violent storms, and the predictability of agriculture could be affected. Some areas and ecosystems may benefit, but the overall impacts for human habitation are troubling. On top of that, feeding 7 billion people depends heavily on fossil fuels (for fertilizer, mechanized agriculture, various other chemicals used in conjunction with high-yield varieties of grain, etc.), so I mention this again mainly because of the impacts of more frequent drought on agriculture, and the effects of agriculture / food production on populations and the likelihood of famine.
• coral bleaching (this can cause the killing of coral reefs in tropical oceans, or less than that radically change the marine ecosystem and the plants and organisms dependent on it) Loss of coral effects all of the ocean life dependent on it, and these are rich and productive parts of marine ecosystems.
• Acidification of the oceans--not good for making shells, not good for any sort of simple life forms highly attuned to the pH, or the more complex forms highly attuned to the food supply coming from simpler forms.
• All of these will affect food production both from fisheries and from agriculture.
• Species extinctions -- this makes sense--climate changes will change environments, change vegetation, and some species will not have the genetic diversity, or the time, to adapt to changing conditions, meaning either migration, or extinction. As habitats change, the mix of species that can survive in a given area changes. Scientsts say we are in the sixth wave of mass extinction in the planet's history. Humans have played no small role in this, because of sheer numbers (it took 150,000 years to get to 1 billion, and another 200 to reach 7 billion) and the displacement of habitat upon which other species co-evolved and depended, and also because of industrial societies' exploitation of fossil fuels and the extra carbon load on the atmosphere and the two main 'sinks'--oceans and forests (especially tropical).
• Spread of diseases -- some species will do better and adapt more quickly. Darwin would bet on critters with short life spans and high reproductive rates, some of which could be harmful bacteria and viruses.
  

Okay, so things look pretty bad. And some of these things aren't problems for our children or grandchildren--they're happening now. As author Bill McKibben puts it, the wave is breaking over our heads, the earth is already changing, and the world in which we grew up will no longer be the same, humans and societies will have to learn to adapt. But are the changes in climates, the threats of sea level rise and greater climate unpredictability the results of natural processes, or humans' activity?

Natural processes, phenomena to consider

Glaciation

We happen to be in an interglacial period--between ice ages. The earth's orbit is complex, and slight variations in its tilt can cause temperatures in the Northern hemisphere to decrease. The result, in terms of a global water cycle, is that more water freezes--a LOT more water. We're talking thousands of feet of ice under Canadian and Northern U.S. cities. If you've ever been on top of Eagle Cap peak, looking down the East Fork of the Lostine River drainage, you know what rivers of ice can do to the landscape (check out Greenland). That means less water reaches the oceans, and ocean levels will drop. The current glacial period in the Northern Hemisphere began about 110,000 years ago, but for the last 10,000 years or so (coincidentally about when human civilizations began to spread and flourish), the planet has been in a glacial recession. When glaciers recede, more snow and ice melts, especially near the poles, and sea levels rise.

Solar radiation, greenhouse effect

The sun's rays, as they reach the earth's atmosphere, have short wavelengths, and most can penetrate. Some heat gets absorbed in the atmosphere, most rays reach the earth's surface--oceans and vegetation hold a lot of heat (deserts are often cold at night because they have so little heat-holding capacity). But what isn't absorbed by the earth's crust re-radiates--bounces off. The wavelengths are longer, though, and generally can't penetrate to leave the atmosphere, and are absorbed by greenhouse gases, such as carbon dioxide, methane, and nitrous oxide. This is the way a greenhouse works--heat penetrates, but can't get back out of the greenhouse--the glass retains most of the heat--enought to keep plants from freezing. Without the greenhouse effect that holds heat in the atmosphere, the surface temperature of the earth would be 0 degrees fahrenheit--all water would be frozen, and we wouldn't be having spring break in Florida or Padre Island.

Energy and the first two laws of thermodynamics

There are two laws of thermodynamics that are important. First, energy can be neither created nor destroyed. That means it isn't really consumed--just transformed into some other form. In the end the transformation is often heat (think of the heat given off by a light bulb). Second, transformation as suggested is usually from a 'higher' to 'lower' quality of energy. When we create order in one place (for instance, building a house--it's a pretty ordered structure), we create slightly more disorder somewhere else--in forests where we cut trees for lumber, mountains where we mined rock for concrete, etc. So unlimited amounts of cheap energy don't really solve all our problems--they could create lots of heat, though.

CO2, nature and humans

Carbon sources, sinks

One of the most important greenhouse gases we talk about is CO2, carbon dioxide. There are natural sources of CO2, that means places where it is produced--animals exhale CO2, when plants respire they release CO2. There are many human sources of CO2--cars, trucks, planes, factories, power plants, etc. There are a couple of important natural sinks of CO2--oceans and plants. Tropical forests are especially important sinks--that is, they can absorb and store lots of CO2. Oceans are the other main sink. One of the key questions is whether we've overburdened these sinks, leading to the release of more CO2 into the atmosphere, and more heat. If you think about fossil fuels as representing ancient forests millions of years old, and incredibly concentrated to boot (not like burning a forest down today--this stuff has been compressed and heated by major geologic forces over millennia), then we're releasing much more into the atmosphere than the earth's system may be capable of handling.

The other two main greenhouse gases are methane and nitrous oxide. The main human sources of methane include confined animal feed operations (CAFOs, such as feedlots for cattle, factory farming of hogs, etc.)and landfills and sewage treatment facilities. Sources of nitrous oxide include fossil fuel combustion, use of nitrogen fertilizer, and clearing of land.A key sink of methane has been permafrost, frozen soil in the arctic region. Now that it's thawing, though, the methane is being released.

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Where are the main sources for CO2? (see the images)

The U.S. is the biggest producer of CO2, pumping billions of tons into the atmosphere annually through various forms. China is close behind (and guess where a large share of their manufactured goods end up?).

The zillion dollar question: Is it humans, or nature?

Consider a few things: There is a great deal more CO2 and other greenhouse gases being emitted into the air since the start of the Industrial Revolution. Those fossil fuels were not 'free.' They required energy from the sun, time, heat, compression--in other words, huge amounts of energy--to become usable for humans. The natural processes of millions of years yielded petroleum. Half of the known reserves have been used up in 200 years. Where did it all go?? So, using fossil fuels, if you pay attention to the first and second laws of thermodynamics, means they'll go somewhere, in some form less usable to humans. What we get are chemical compounds with amazing heat-holding capacity, stuck in our atmosphere for a century or more. Meaning, also, that what is produced today will have effects for generations to come.

Since discovering concentrated forms of energy--the fossil fuels--humans have burned them at an increasing rate of consumption for over 200 years. Evidence suggests that average global temperatures have increased in the last hundred years, and that the amount of CO2 in the atmosphere has risen quite dramatically over the same period. Logic and observation suggest that humans are having an impact on the greenhouse effect--essentially putting more heat into the atmosphere. Oceans also have great heat holding capacity--they take up 3/4 of the earth's surface, and it doesn't take a large increase in temperature to create some major changes.

NASA has a site separating natural and human impacts on global warming (go down the page a bit to the 'anthropogenic' sources). Other so-called 'skeptics' take a different approach (like the Cato Institute, ridiculing those calling for CO2 reductions by referring to carbon dioxide as a 'satanic gas').

There are scientists who contend that solar variation and long-term cycles may be playing out, but are masked by human activity.

In the end, it's just really fantasy to say the laws of thermodynamics don't matter, and the billions of tons of carbon pumped into the atmosphere, combined with the compromising of oceans' and forests' capacities to sequester it, don't matter. But even if you want to believe--and it takes faith (that means believing in things unseen)--that humans aren't accelerating natural processes, there is still the fallout from warming to which societies will have to respond.