Monday, August 29, 2016

Humans have caused climate change for at least 180 years

As part of my video project, I have created a graph that compares the big changes triggered by the ingenuity of the Industrial Revolution and the increase in atmospheric CO2.  This graph will be animated and the central focus surrounds the first mathematical description of the relationship between CO2 and changes in climate first postulated by Svante Arhennius in 1896.  If we date the start of the Industrial Revolution at 1750, the changes had been happening for 146 years before a Nobel winning chemist noticed them.  Interestingly, those 146 years had only increased atmospheric CO2 by about 20 ppm.  That is roughly the same amount as the increase since 2004.  No wonder it required a world-class chemist to figure it out back then.

The CO2 levels are indicated by the yellow line with the light blue fill underneath.  Click to enlarge.

As research methods and instrumentation have gotten better, it now seems pretty obvious that the climate started to change almost as soon as humans got serious about burning coal.  Which makes perfect sense when you think about it.  After all, coal is a form of carbon that had been put into long-term storage before humans discovered all the useful things that could be done with those dirty rocks.

Humans have warmed the planet for 180 years

Oleg Ködding-Zurmühlen, 24.08.2016

Climate change is usually thought of as a 20th- and 21st-century phenomenon. But new research has found that the planet has been heating up since the dawn of the industrial revolution.

Man-made climate change began 180 years ago - much earlier than previously assumed, according to a new study by an international team of researchers.

This is the first time climate records from locations across the northern and southern hemispheres were analyzed side-by-side, explains Jens Zinke, a paleontologist at the Free University of Berlin und co-author of the study.

The researchers from Australia, the USA, Europe and Asia investigated data from tropical corals, sediment cores, stalagmites, tree rings and ice cores, and compared them with climate model simulations spanning thousands of years.

Climate change began with the industrial revolution

"The analysis shows that global warming began in connection with rising levels of greenhouse gases as a result of the industrial revolution," Zinke told DW.

Even the relatively small amount of greenhouses gases released into the atmosphere at the beginning of the industrial revolution quickly affected the earth's climate.

Nerilie Abram, climate scientist at the Australian National University in Canberra and lead researcher on the study, described the findings as "extraordinary".

"It was one of those moments where science really surprised us. But the results were clear. The climate warming we are witnessing today started about 180 years ago."

Abram said man-made climate change has generally been discussed as a 20th century phenomenon because climate measurements from before the 1900s are hard to come by.

Tropical oceans and the Arctic heat up first

The study found that global warming began in the Arctic and tropical oceans as early as the 1830s. "In the northern hemisphere, the Arctic in particular is very sensitive to climate change," Zinke said.

The warming of large parts of the southern hemisphere followed up to 50 years later, according to the data. The scientists say this is due to regional differences in ocean currents.

The northward flow of warm currents in the southern hemisphere meant Antarctica long avoided significant effects of climate change.

"The strength of the study lies in the fact that we have data from individual regions of the planet. We have exact data - for example places where tropical corals occur - and can say when global warming got going there," said Zinke.

Climate records hidden in coral

Zinke's team analyzed tropical corals in the Indian Ocean, the Caribbean and the Indonesian archipelago.

"Tropical corals continue to grow for up to 400 years. Through the rapid growth of one to two centimeters per year, you can analyze them from month to month over many decades and centuries."

Like trees, corals have rings of annual growth. To get data accurate to a single month, researchers used a dental drill to take minute samples.

Implications for the future

The scientists said their findings had important implications for our understanding of the extent to which humans have - and will - impact the global climate.

"To make better predications, studies must take even the 19th century into consideration," Zinke said.

The rapid warming in the early stages of the industrial revolution imply that small changes in levels of greenhouse gases can have a significant impact, the scientists said.

And that might also offer hope of similarly speedy "paybacks" from climate change mitigation efforts. more

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