Confusion reigns around the terms "global warming" and "climate change." I often see gleeful blog comments from climate-change deniers to the effect of, Scientists are so unsure of global warming that they're now calling it "climate change." Here's a little clarification.

Climate change refers to long-term change in Earth's climate, which has multiple effects. One of these is global warming, that is, the change in average surface temperature. According to virtually every climatologist and scientific association, global warming is mainly caused by increasing levels of carbon dioxide, a "greenhouse" gas resulting from burning fossil fuels such as coal, natural gas and oil.

Most attention focuses on the warming aspects of CO2-induced climate change, about two degrees Fahrenheit in the last 150 years. This is unfortunate, because unusually cold weather offers stubbornly defiant politicians, such as Sen. Jim Inhofe (pictured above with snowball), the opportunity to "prove" global warming is a hoax, thereby sabotaging meaningful political action.

While the overall trend is toward warming, climate change of the sort we're now getting used to ("The Future Weather is Now," March 19) causes extreme swings in weather. For instance, warm and dry drought weather in California is typically matched by cold and wet polar vortex conditions on the East Coast (think of a fridge, where the cold inside is counterbalanced by the warm condenser coils at the back), so, ironically, Inhofe's snowball-in-February stunt demonstrated climate change. Global warming is responsible for other alarming trends, such as:

Rising sea levels, which are caused both by ocean warming (since warm water occupies greater volume than cold) and ice cap and glacier melting. At the present rate, this century will see Earth's oceans rise about a foot (conservatively — the rate is accelerating). Island nations such as Tuvalu and the Maldives already feel the effects; Miami isn't far behind, especially as a warmer atmosphere makes events like hurricanes Katrina and Sandy more likely.

Decreasing fresh water. We're seeing this in California as we enter our fourth year of drought (unprecedented in the last 1,200 years), where the Central Valley water table depth is dropping precipitously; thousand-foot-deep irrigation wells — unheard of a generation ago — are now commonplace. Rising sea levels also lead to salinization of groundwater and estuaries, thus contaminating traditional sources of fresh water.

Disruption of coral reefs. Coral reefs occupy 1 percent of the ocean floor, but are home to a quarter of all marine species and some 500 million people living in the tropics depend on them for survival. However, many species of coral are stressed to the point of dying, unable to adapt to warming ocean water. Currently about 10 percent of coral reefs are dead, with another 60 percent at risk.

Population instability. When a people's food and water supply is threatened, myriad problems arise, including conflict and war, disease and infant mortality, economic stress and poverty, refugees and migration (particularly from rural areas to cities).

And yet global warming may not be the worst consequence of climate change. Next week, we'll be looking at its "evil twin," ocean acidification.

Barry Evans (barryevans9@yahoo.com) worries about the world Sen. Inhofe will leave to his 20 children and grandchildren.