Blood group: An inherited feature on the surface of the red blood cells. A series of related blood types constitutes a blood group system, such as the Rh or ABO system. The frequencies of the ABO and Rh blood types vary from population to population.lood group: An inherited feature on the surface of the red blood cells. A series of related blood types constitutes a blood group system, such as the Rh or ABO system. The frequencies of the ABO and Rh blood types vary from population to population.
October 22, 2009. Running time 1:26. Climate scientists explain why theyâre sure the primary cause of global climate change today is increasing human emission of greenhouse gases â mainly carbon dioxide. Skip to main content
How do we know that humans are the major cause of global warming? Photo: freeimage4life/Flickr We all know that warmingâand coolingâhas happened in the past, and long before humans were around. Many factors (called âclimate driversâ) can influence Earthâs climateâsuch as changes in the sunâs intensity and volcanic eruptions, as well as heat-trapping gases in the atmosphere.