Seeing the environmental forest

There is a persistent idea floating around in some circles that the current episode of global warming is due to some sort of natural cycle.  Why not?  Previous episodes of global warming or cooling were natural.  Beyond the data that shows that this episode of global warming is due to CO 2 , the main problem with that idea is finding a natural cycle fits.

A couple days ago, a fellow user on a different forum challenged me with the following information while disputing whether or not the Earth is still warming:

One of the basic tenants of ecology is that climate determines the type of vegetation present in any location and vegetation determines the type of insects, birds, mammals, etc.  Average rainfall and average temperature are particularly important.  One of the widely republished and modified diagrams on the effects of rainfall and temperature comes originally from R. H. Whittaker's book Communities and Ecosystems :

I've run across several skeptic claims recently that Arctic sea ice extent is within the normal range for this time of year, as well as claims that Antarctic sea ice is growing  While both are true, the implication that we shouldn't be concerned with the Arctic sea ice melting because of those facts is pure nonsense.

One of the claims by climate skeptics is that global warming is due to natural cycles, most commonly the Pacific Decadal Oscillation (PDO).  The claim is that positive PDO phases lead to warming whereas negative PDO phases lead to cooling.  There are multiple problems with this claim, from ignoring how the PDO is calculated to ignoring the laws of physics.

Since global surface and atmospheric temperatures have flatlined over the past 7 years (see graph of UAH temperatures below), there's some noise over whether or not global warming has stopped.

from climate skeptics is that the Earth hasn't warmed since 1998.  Why 1998?  Because that is the only start point that allows them to make that claim.  First, here's a graph of UAH since 1993, plotted to the 1981-2010 baseline and with a loess regression trend to highlight the trend:

In the last three posts, I've examined the evidence that the Earth is warming and that the warming is due to CO 2 .  Continuing this series, today I'll look at the evidence that shows that humans are behind the increase in CO 2 .

After Joseph Fourier deduced the existence of the greenhouse effect in the 1820s, it took until 1861 before John Tyndall identified the first components of the greenhouse effect as water vapor and CO 2 ( Tyndall 1861 ).  One hundred fifty-two years of research later, we know far more about the absorptive properties of  CO 2  and other greenhouse gases , including water vapor, including how they affect Earth's infrared spectrum.

The existence of Earth's greenhouse effect was first postulated by Joseph Fourier in the 1820s, when he calculated that the Earth should be much colder than it actually is.  Using the Stefan-Boltzmann law, and modern measurements, we can calculate what that temperature should be.  The equation for doing so is