page_title: Climate variability and change
section_title: Life
hierarchical_section_title: Climate variability and change / Consequences of climate variability / Life
caption_attribution_description: English: During the Last Glacial Maximum 14000 years ago, thermal-driven evaporation from the oceans onto continental landmasses was low, causing large areas of extreme desert, including polar deserts (cold but with low rates of precipitation). Greater precipitation today creates a much different distribution of climatic zones, although anthropogenic changes including agriculture prevent forest cover from reaching its theoretical potential. Near the start of the Atlantic Period, 8000 years ago, the world's climate was warmer and wetter than today according to an ORNL estimate.
context_page_description: Climate variability includes all the variations in the climate that last longer than individual weather events, whereas the term climate change only refers to those variations that persist for a longer period of time, typically decades or more. In the time since the industrial revolution the climate has increasingly been affected by human activities that are causing global warming and climate change.
  The climate system receives nearly all of its energy from the sun. The climate system also radiates energy to outer space. The balance of incoming and outgoing energy, and the passage of the energy through the climate system, determines Earth's energy budget. When the incoming energy is greater than the outgoing energy, earth's energy budget is positive and the climate system is warming. If more energy goes out, the energy budget is negative and earth experiences cooling.
  The energy moving through Earth's climate system finds expression in weather, varying on geographic scales and time. Long-term averages and variability of weather in a region constitute the region's climate.
caption: Top: Arid ice age climateMiddle: Atlantic Period, warm and wetBottom: Potential vegetation in climate now if not for human effects like agriculture.[100]
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