La Nina is once again going lead to cooler temperatures this year but that doesn't mean that the earth isn't warming overall.
"When you look at climate change you should not look at any particular year," he (The World Meteorological Organization's secretary-general, Michel Jarraud) said. "You should look at trends over a pretty long period and the trend of temperature globally is still very much indicative of warming.But just you wait, the Republicans and other climate change deniers will seize on this summer's cooler temperatures to tell us again that anti-business liberals are just making this up. Michelle Bachmann will come up with something about how its all just made up by the CFL manufacturers.
"La Nina is part of what we call 'variability'. There has always been and there will always be cooler and warmer years, but what is important for climate change is that the trend is up; the climate on average is warming even if there is a temporary cooling because of La Nina."
Now I don't expect all of my elected officials to understand the quantum physics behind how CO2 converts infrared radiation to heat (I only just understand it), but I do expect them to be humble enough to not blow their mouths off about things they really don't understand. In my more cynical moments I'm sure that the strong ego and thick skin needed to run for national office kills off any naturally occurring humility that might be in them.
Enough of that, back to the science. La Nina and El Nino, as Jarraud says, are natural variations. Global warming and the resulting climate change are long term changes due to levels of CO2 in the atmosphere that don't seem to have occured in the past 400,000 years. (For a sense of scale, the last ice age ended 12,000 years ago.) My question is how are the El Nino and La Nina events changing as the global mean temperature rises? How the ocean temperatures will change as the air temperature changes is not clear. Will the Pacific Ocean be even warmer in El Nino and even colder in La Nina, or will the difference get smaller so that the effect gets smaller? Or will the events happen more often?
The problem we run into here is how far back our data goes. We've got air temperature readings in the US going back to the Civil War, but we've only been taking satellite readings of the temperature of the oceans for a few decades at most. We just don't know exactly whats going to happen, we have more questions than answers, and I have to admit that it scares me sometimes.