Land-ocean temperature index, 1880 to present, with base period 1951-1980. The solid black line is the global annual mean and the solid red line is the five-year lowess smooth. The blue uncertainty bars (95 percent confidence limit) account only for incomplete spatial sampling. (This is an update of Fig. 9a in Hansen et al. (2010).)

One constant refrain from the usual suspects goes that the climate has always changed, so why worry about it now? There are a lot of answers to that. My favorite is to ask them, since smoking has been causing cancer for millennia, why worry about your kids smoking now? Regardless, like most instances of fraudulent pseudo-science, there’s an element of truth to the climate’s-always-been-changing refrain, and that’s why it’s deployed by fossil fuel apologists.

A new study has found that climate has indeed been changing for a long time, on human timescales anyway, and concludes that some of those longer term trends are attributable to human activity:

The new study, just out on Wednesday in the journal Nature, suggests human-caused, or anthropogenic, climate change has been going on for decades longer than existing temperature records indicate. Using paleoclimate records from the past 500 years, the researchers show that sustained warming began to occur in both the tropical oceans and the Northern Hemisphere land masses as far back as the 1830s — and they’re saying industrial-era greenhouse gas emissions were the cause, even back then.

Paleo-Climatologist Michael Mann, co-creator of the Hockey Stick climate record, posted a few thoughts on the new study on his own site. And he responded via email saying,” While I differ with the authors on some of the interpretation (our own work shows that climate models do in fact pick up the early response to human-caused CO2 increases), the work does once again underscore the unprecedented nature of the warming caused by ongoing fossil fuel burning.”

We’ve only been keeping detailed, instrument records over a broad enough swath of the planet to be confident about global temperatures since the latter part of the 19th century. That’s why charts like the one above from NASA’s GISS climate unit start in 1880. And we see immediate staggering noise in global temperature followed by a series of jagged upticks. So it’s no surprise that even earlier activity, which included nearly continual warfare across Eurasia, the start of the industrial revolution, and massive deforestation everywhere from Canada to Australia, could tip the delicate balance of greenhouse gasses and thermal exchange toward a warmer planet.