a warming in the lower atmosphere, confirming the action of the greenhouse effect and ozone depletion. Observed regional climatic variations confirm predictions concerning ongoing changes, for example, by contrasting (smoother) year-to-year global variations with (more volatile) year-to-year variations in localized regions. Conversely, comparing different regions' warming patterns to their respective historical variabilities, allows the raw magnitudes of temperature changes to be placed in the perspective of what is normal variability for each region. Regional variability observations permit study of regionalized climate tipping points such as rainforest loss, ice sheet and sea ice melt, and permafrost thawing. Such distinctions underlie research into a possible global cascade of tipping points. See also Climatological normal Anthropocene Notes References (pb: ). . External links Global Climate Change from NASA (US) Intergovernmental Panel on Climate Change (IPCC) Climate Variability – NASA Science Climate Change and Variability, National Centers for Environmental Information Climate and weather statistics History of climate variability and change Articles containing video clips Climatology Natural environment