The first six months of 2010 brought a string of warmest-ever global temperatures, but connecting these dots to long-term climate change patterns remains frustratingly difficult, experts say.

Not only was last month the hottest June ever recorded, it was the fourth consecutive month in which the standing high mark was topped, according to the US National Oceanic and Atmospheric Administration (NOAA)…

But making a direct link between year-on-year variations in the weather and changes in climate — best measured in centuries — is simply not possible, scientists say…

For scientists, he said, it would be like trying to figure out which way the tide is moving by watching only a few waves lapping at the shoreline.

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Asked by researchers conducting a 1990s survey on air conditioner usage why she left hers turned off, a California apartment resident responded, “Because it makes it too hot outside.” She had a point. With less exposure to heat, studies show, our physical and mental tolerance for heat declines — and our fondness for the air conditioner grows…

Air conditioning buildings and cars in the United States has the climate impact of half a billion metric tons of carbon dioxide a year. That exceeds the total annual carbon dioxide emissions of any one of these nations: Australia, France, Brazil or Indonesia. In an effort to reduce energy use and curb greenhouse emissions, industry and government are pursuing more efficient cooling technologies for cars and buildings. But greater efficiency can’t reverse the unsustainable living, working and transportation patterns that air conditioning has helped foster.

Greener building designs that favor natural ventilation will help, but in the millions of existing homes, workplaces and schools that we’ll be using for decades to come, the most important adjustment will be not in our thermostats but in our own comfort expectations…

In other words, we need to back out of the ecological dead-end alley we’ve been traveling down for half a century. It won’t be easy. With air conditioning so thoroughly integrated into American society, we’re going to have trouble finding reverse gear. But it’s there.