What evidence is there that climate change is caused by human activities, and what are the potential consequences?

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ophelious eNotes educator| Certified Educator

Despite persistent naysayers, the evidence is pretty strong that human beings are having an impact on the Earth's climate.  This is because human beings are doing things that throw the planets thermostat, one calibrated over a long period of time, out of whack.

Here are some of the ways that humans are changing things, all of which can be measured.  These first ones fall under the category of "greenhouse gasses," which make the planet warmer by essentially covering it in a blanket:

  • Carbon dioxide in the air has been increasing since about 1700, the same time as machinery began to play a bigger role in our societies.  80% of that increase, though, can be attributed to the industrialization of the 1900's.  The more we burn, the more is released.  The burning of the rain-forests for farmland releases massive amounts of the stuff. 
  • Ozone is another gas that is produced by chemical reactions in the atmosphere.  Humans don't make these reactions happen, but humans put the gasses, such as carbon dioxide, into the air in the first place.  More gasses mean more reactions, which mean more ozone.
  • Methane, the byproduct of cattle farming, has been increased by the large scale production of these animals.
  • Halo-carbon gasses, such as those that used to be used in air conditioners,
  • Aerosols
  • Water vapor.  Though humans don't create much of this directly, the warming of the oceans that results from other greenhouse gasses creates we do create leads to more evaporation.

All of these, though naturally occurring, have been increased by human production and consumption.  This has caused temperatures to notch slightly higher.  This leads to more evaporation, along with the melting of polar ice.  Polar ice has large quantities of trapped methane, and when it is released the process becomes self-fueling.

Aside from greenhouse gasses, humans influence local climates can't be denied.  The replacing of dirt with concrete to create major cities greatly changes the way heat is retained and radiated back into the atmosphere.  The destruction of forests in order to create arable land releases carbon and reduces the ability of the planet to act as its own air cleaner.  The consumption and diversion of fresh water changes local climates and leaves some areas hotter and dryer, destroying soil and expanding deserts, which surprisingly endure massive temperature shifts throughout the day.

As for the impact this will have:

  • Rising temperatures melt polar ice.  Polar ice floods the sea, both increasing its level and cooling it down.  Increased water levels will flood coastal areas.
  • A hotter planet evaporates water more quickly, resulting in less water resources.  This is also true because a hotter planet makes less snow, and snow-melt is what a lot of rivers depend on to exist.
  • Animals will shift the areas they live in, and some will thrive while others (like polar bears,) will struggle to survive.
  • Deserts will expand.
  • Weather patterns will become more extreme and erratic.  A warmer planet will fuel tornadoes, hurricanes, and other storms.
  • Droughts will result in famines.

These are just some of the impacts of climate change.  In the 50's, there was much talk of the possibility of a "nuclear winter" that would freeze us all, but not much of the "greenhouse summer" we have actually found ourselves in.