The debate regarding whether climate change is caused by human activity or is a natural repeating occurrence just heated up. Three studies published this week in the journal Nature and Nature Geoscience claim to prove that the current global increase in temperature is unprecedented. According to NASA, the scientific consensus is that "Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that the greenhouse gases emitted by human activities are the primary driver."
A study published in Nature found that “the warmest period of the past two millennia occurred during the twentieth century for more than 98 percent of the globe. This provides strong evidence that anthropogenic global warming is not only unparalleled in terms of absolute temperatures, but also unprecedented in spatial consistency within the context of the past 2,000 years.”
This suggests that the current warming of two degrees fahrenheit per year isn’t just another naturally occurring shift in Earth’s climate. In commentary about the new papers, Scott St. George, a physical geographer at the University of Minnesota in Minneapolis wrote, “The familiar maxim that the climate is always changing is certainly true. But even when we push our perspective back to the earliest days of the Roman Empire, we cannot discern any event that is remotely equivalent — either in degree or extent — to the warming over the past few decades. Today’s climate stands apart in its torrid global synchrony.”
The second study published in Nature Geoscience concluded another explanation for the past fluctuations is likely due to volcanic eruptions. “All the eruptions were followed by substantial drops of summer temperature over the Northern Hemisphere land areas. In addition to the direct radiative effect, which lasts 2–3 years, the simulated ocean–atmosphere heat exchange sustained cooling for several years after these eruptions, which affected the slow components of the climate system.” This has become particularly pronounced since the late 20th century. The third study notes that the temperature increase over two decades or longer have been the most rapid in the past two millennia.
According to NBC MACH, one of the teams led by Raphael Neukom, a postdoctoral researcher at the University of Bern’s Institute of Geography in Switzerland, analyzed 2,000 years' worth of climate data. In the absence of direct temperature information — thermometer measurements were scarce before the middle of the 19th century — the scientists looked at data on old trees’ growth rings, layers of glacier ice and the remnants of corals, whose layers have different chemical compositions depending on the temperature of seawater.
According to Reuters, Mark Maslin, professor of climatology, at University College London said the paper should “finally stop climate change deniers claiming that the recent observed coherent global warming is part of a natural ...cycle.”
Stefan Brönnimann, one of the authors from the University of Bern and the Pages 2K consortium of climate scientists told the Guardian, “There is no doubt left – as has been shown extensively in many other studies addressing many different aspects of the climate system using different methods and data sets.”
Despite what looks to be complete agreement across the science community, there are still a small number of scientists resisting the findings. On July 14th, the Helsinki Times published an article saying a Finnish research team “suggests that even though observed changes in the climate are real, the effects of human activity on these changes are insignificant. The team suggests that the idea of man made climate change is a mere miscalculation or skewing the formulas by the Intergovernmental Panel on Climate Change.
An alternate theory cited in the article from a Japanese led research team from Kobe reads, “When galactic cosmic rays increased during the Earth’s last geomagnetic reversal transition 780,000 years ago, the umbrella effect of low-cloud cover led to high atmospheric pressure in Siberia, causing the East Asian winter monsoon to become stronger. This is evidence that galactic cosmic rays influence changes in the Earth’s climate.”