A team of climatologists with members from the U.S., Australia, Canada and Norway is claiming in a paper they've had published in the journal Proceedings of the National Academy of Sciences, that they have found proof that global warming is being caused by human influences. They are basing their claims on computer simulations they've run and data obtained from three decades' worth of satellite observations.
Most of the world's scientists agree that our planet is experiencing global warming. Most also generally support the theory that the cause of global warming is due to an increase in greenhouse gasses, primarily carbon dioxide. And while many also support the notion that the increase in greenhouse gasses in the atmosphere is likely due to human emissions, few are willing to go on record claiming that global warming is due directly to human activities. The researchers in this new effort are one such group and they claim they have proof.
Satellites, as most everyone knows, have been hovering over or circling our planet for over half a century. Over that time period they have grown progressively more sophisticated, measuring virtually every conceivable aspect of the planet below—from gas levels in the atmosphere to temperature readings on an averaged global scale, to the impact of natural events such as volcanic eruptions. It's this data the researchers used in their attempt to root out the true source of global warming.
The research team conducted a two stage study. The first involved creating computer models that simulated climate evolution over the past several decades under three different scenarios: a world without human influence, a world with only human influence and a world without human emissions or naturally occurring incidents such as volcanic eruptions. The second stage involved gathering data from satellites and comparing it with what the team had found in creating their simulations. They say patterns emerged that prove that human influence is the cause behind global warming. One example they cite is data that shows that the troposphere (the part of the atmosphere closest to us) has seen a steady rise in temperature over the past several decades, even as the layer just above it, the stratosphere, has cooled slightly.
But what has the team really convinced that humans are the true source behind global warming, is that they were unable to produce the type of warming we've seen with just natural events—it's only when human emissions are added to models that such a trend can be realistically simulated. That, they say, proves that human practices over the past several decades are responsible for global warming.