A World Never Before Experienced by Humans

by Paul Mayewski

The vast majority of scientists understand the human origins of the rapid, recent rise in greenhouse gases. Even most of the skeptics accept that there has been a rise, debating only the cause and the consequences. But, if recent greenhouse gas rise is not caused by human activity then it is extremely odd that so many other undeniably human components of the atmosphere have also increased dramatically in the industrial era along with greenhouse gases. Ice cores offer robust records of how the atmosphere has changed over thousands and hundreds of thousands of years, and they have given us a detailed view of how it has changed with the advent of human industrialization. The illustration below, taken from the Climate Change Institute’s report on climate change prepared for the State of Maine, highlights the dramatic increases in an amazing range of chemicals over the last century. Though this figure only goes back 5,000 years, the recent, dramatic industrial rise still stands out over the last several million years.
Why does any of this matter?

• Every single one of the components in the illustration below has an impact on human health; either directly or through the impacts on the ecosystems we depend on.
• While greenhouse gases stay in the air for a long time, at least hundreds of years, other pollutants including toxic metals, acid rain, and particulates are washed out in just days or months so efforts that reduce emissions of these compounds lead to healthier air right away.
• Because greenhouse gas emissions are directly tied to sources for toxic metals, acid rain, particulates and other pollutants reductions in any of the latter also result in reductions in greenhouse gases. A win-win situation.

Compared to the last 5,000 years, human industrialization has dramatically changed the composition of the atmosphere. Even if we extend the plot to millions of years, the industrial rise is still a radical departure. Plot from Maine’s Climate Future.