It took me no effort to come up with the answer to that question, and I was able to state the answer in one sentence:
Because we no idea what to expect.
The article agrees with me, but the writer had a lot more difficulty saying it. Stephen Schwartz of Brookhaven National Laboratory offered two reasons that the globe has "only" warmed 1.4 degrees Centigrade (rather than 3.8):
- Earth's climate may be less sensitive to rising greenhouse gases than currently assumed.
- Reflection of sunlight by haze particles in the atmosphere may be offsetting some of the expected warming.
The first one says that we don't know how much greenhouse gases warm the globe. The second says that maybe sunlight is being reflected by haze particles in the atmosphere.
Yes, and maybe there's a lot of other influences that we don't understand.
Have they forgotten that their very own publication, Science Daily, reported less that 4 years ago that scientists were surprised to find out that living plants emit methane, a greenhouse gas 21 times more potent than carbon dioxide?
Have they forgotten that this unknown methane source was emitting 10 to 30 percent of all methane in the atmosphere?
Come on, folks. That article reported that though scientists thought only dead plants emit methane. It turns out that living plants emit 10 to 1,000 times more than dead plants.
Listen, I'm all for limiting—or better preventing altogether—the amount of carbon dioxide we're putting in the atmosphere. It turned out that chlorofluorocarbons hurt the ozone layer. We stopped putting CFC's in spray cans.
Those sorts of things are great ideas.
However, running around trying to explain why your wild, not-yet-educated guess about the extent of global warming is a waste of time. We all know. We just don't understand climate that well. Maybe some day we will, but today we don't.
Climate Change Is Not Well Understood
Let me say again. I'm all for limiting CO2 emissions. The fact that we don't understand climate change is reason not to mess with the climate, and burning the carbon out of the ground and putting it in the air is messing with the climate.
Real bad idea.
However, making uneducated guesses about the amount of climate change, then having them be wrong, won't help the case for limiting CO2 emissions.
This Times article says this about scientific opinion:
Many scientists believe that we need to at least stabilize carbon concentrations at 450 p.p.m. to ensure that global temperatures don't increase more than about 2 degrees Celsius above the pre-industrial level.
Obviously, these "many scientists" weren't expecting 3.8 degree Celsius increases in global temperature. CO2 levers aren't expected to hit 450 ppm, according to that same article, until about 2038.
Even more pertinent is the uncertainty page at climate.NASA.gov. I like NASA's web site. It has proven to be remarkably unbiased in it's reporting, and it always has access to the latest data.
Their page lists numerous things we don't understand yet, saying things like:
Climate scientists do not have much confidence that they understand longer-term solar changes.
Aerosol forcing is another substantial uncertainty in predictions of future climate.
You can read the rest of that page for yourself.
Does Uncertainty About Climate Change Matter?
It should spur us to action. We don't understand climate change enough to make predictions about it. Making false predictions doesn't help the cause.
What's the cause?
Mankind is taking immense amounts of carbon out of the ground in the form of fossil fuels and burning it to put it in the atmosphere. Bad idea! Very bad idea!
I read a complaint about something said by Vicky Pope of the UK Meteorological Office. She said:
Anything that alters the climate in a different way from reducing carbon has inherent dangers because we don't understand the climate well enough.
The fact is, this is the truth. We don't understand the climate well enough to be messing with it.
Reducing carbon emissions is not messing with the climate. Reducing carbon emissions is ceasing to mess with the climate.