For instance, Phoenix has a "Continental Tropical" climate which means it is usually hot and dry. If it's cold on a January morning in Phoenix, this does not change the climate; it only speaks to the weather of the day.

Therefore, please don't make the unscientific mistake often heard on the street: "I know global warming isn't true because it snowed in Florida. I saw it on the news". Or conversely, "I know people are causing global warming because there was record heat in Cleveland all of last week".

These are examples of weather events and are not climate changes.

Now, if we can PROVE that the climate has consistently changed (gotten colder, hotter, or what have you) because of increased greenhouse gases, then that's a different story. But no one has done that. What we see instead are valid observations, such as ice calving and arctic sea ice decreasing, but what does this actually tell us? It merely points to a warming, not to a cause. So a summer heat wave in 2000 can no more be used to "sell" human-induced global warming than can Chicago's record cold in January 2009 be used as a pitch-man for global cooling.

Even if the warming were shown to be warmest ever (which it hasn't), this does nothing to prove human causation. Furthermore, the alarmist rhetoric about polar bears is effective at tugging on our heartstrings but it is a straw man argument. The arctic has periodically warmed and cooled to levels at least as warm in the past, and somehow these "endangered" bears survived.

Data shows the Arctic was as warm in the 1930's as it is today, yet the bears endure. Indeed, newer studies show the bear population increasing.

Also of note: we only have good icecap (satellite based) data since 1979. With such a short database, we're only confirming that we're in a climate phase which has trended warmer in the past 30 years, nothing more. In fact, the Earth's temperature has generally cooled a bit since the year 2000.

If the warming since 1980 is really human caused, you would expect to see this spiral steadily upward as CO2 increases, becoming worse and worse. But we do not see this. We see a warmer-cooler-warmer pattern, which amplified some in the late 20th Century. But this has happened before. So whatever warming we might be causing is still trumped by natural variation.

Perhaps anthropogenic gas emissions contribute some degree to climate change; This is probably small compared to natural cycles and human land-use change effects.

Belief is irrelevant for this issue: let's focus on science. When the data conclusively shows a link and not just a partial correlation, then it will be easy to accept the anthropogenic greenhouse gas theory as completely true.

Learn more about this author, Cameron Foster.
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