Pre-industrial anthropogenic CO2 emissions: How large?

Guest article by William Ruddiman Fifteen years after publication of Ruddiman (2003), the early anthropogenic hypothesis is still debated, with relevant evidence from many disciplines continuing to emerge. Recent findings summarized here lend support to the claim that greenhouse-gas emissions from early agriculture (before 1850) were large enough to alter atmospheric composition and global climate substantially. Marine isotopic stage (MIS) 19 is the closest orbital analog to the current MIS 1 interglaciation (Tzedakis et al., 2012), with similarly small changes in precession (εsinω) and nearly

Non-condensable Cynicism in Santa Fe

Guest Post by Mark Boslough The Fourth Santa Fe Conference on Global & Regional Climate Change will be held on Feb 5-10, 2017. It is the fourth in a series organized and chaired by Petr Chylek of Los Alamos National Laboratory (LANL) and takes place intervals of 5 years or thereabouts. It is sponsored this year by LANL’s Center for Earth and Space Science and co-sponsored by the American Meteorological Society. I attended the Third in the series, which was held the week of Oct 31, 2011. I reported on it here in my essay “Climate cynicism at the

Boomerangs versus Javelins: The Impact of Polarization on Climate Change Communication

Guest commentary by Jack Zhou, Nicholas School of the Environment, Duke University For advocates of climate change action, communication on the issue has often meant “finding the right message” that will spur their audience to action and convince skeptics to change their minds. This is the notion that simply connecting climate change to the right issue domains or symbols will cut

The Early Anthropocene Hypothesis: An Update

Guest post from Bill Ruddiman, University of Virginia For over a decade, paleoclimate scientists have argued whether the warmth of the last several thousand years was natural or anthropogenic. This brief comment updates that debate, also discussed earlier at RC: Debate over the Early Anthropogenic Hypothesis (2005) and An Emerging View on Early Land Use (2011). The graph below outlines the evolution of that debate through 4 phases. In phase 1 (the 1900’s), scientists viewed Holocene climate change as driven only by natural causes until the industrial era began. But by the late 1990’s, ice core data revealed late Holocene

How Likely Is The Observed Recent Warmth?

With the official numbers now in 2015 is, by a substantial margin, the new record-holder, the warmest year in recorded history for both the globe and the Northern Hemisphere. The title was sadly short-lived for previous record-holder 2014. And 2016 could be yet warmer if the current global warmth persists through the year. One might well wonder: just how likely is it that we would be seeing these sort of streaks of record-breaking temperatures if not for human-caused warming of the planet? Precisely that question was posed by several media organizations a year ago, in the wake of the then-record 2014 temperatures. Various press accounts reported odds

An Online University Course on the Science of Climate Science Denial

Guest post from John Cook, University of Queensland For many years, RealClimate has been educating the public about climate science. The value of climate scientists patiently explaining the science and rebutting misinformation directly with the public cannot be overestimated. When I began investigating this issue, my initial searches led me here, which was invaluable in increasing my understanding of our climate and making sense of misinformation. RealClimate has inspired and empowered a host of climate communicators such as myself to step forward and help make climate science more accessible to the general public. To further the work of educating the public, and empowering people to communicate the realities of climate change, the Skeptical Science team has

Climate Oscillations and the Global Warming Faux Pause

No, climate change is not experiencing a hiatus. No, there is not currently a “pause” in global warming. Despite widespread such claims in contrarian circles, human-caused warming of the globe proceeds unabated. Indeed, the most recent year (2014) was likely the warmest year on record. It is true that Earth’s surface warmed a bit less