TURNING THE CLIMATE CLOCK BACK 3.3 MILLION YEARS

"BY 2025, CO2 LEVELS WILL BE HIGHER THAN THEY'VE BEEN FOR THE LAST 3.3 MILLION YEARS" [Nature Scientific Reports July 10, 2020]

Let's see. What was going on 3.3 million years ago?

--Humans like us were just a gleam in evolution's eye. The most promising potential ancestor around then was Australopithecus, an apelike creature living in southern Africa who may have been the first to use shaped stones to smash open bones for their marrow. 

--Earth wouldn't enter the current geologic epoch, the Holocene, for another 3,288,000 years. It was then in the middle Pliocene. 

--North and South America hadn't yet collided and connected. 

--North America sported two elephant-like species, hyenas, small, three-toed ancestors of modern horses, bone-crushing dogs, giant bears and three species of huge, saber-toothed cats. 

Smilodon populator--one of North America's

Pliocene saber-toothed cats

Credit: Charles Knight/American Museum of Natural History

--Humans wouldn't set foot on the continent for another 3.27 million years.

--Crucially, from our point of view, atmospheric CO2 levels were comparable to today's (somewhere between 381 and 427 parts per million), yet global temperatures were 2 to 3 degrees C (3.6 to 5.4 degrees F) higher than they are now, and sea levels were 25 meters (82 feet) higher. 

Equally crucially, because of those nearly equal CO2 levels, the period tells us what our world may look like all too soon.  "We studied this particular interval in unprecedented detail because it provides great contextual information for our current climate state," says Elwyn de la Vega, researcher at the University of Southampton's School of Ocean and Earth Science, in the UK, and lead author of the Nature Scientific Reports study.

The Southampton research team was able to pin down those ancient CO2 levels by studying the fossilized shells of foraminifera--millimeter-sized sea creatures protected by carbon-rich shells. The ratios of boron isotopes in the shells correlate with atmospheric CO2 levels at the time the shells formed.

Clearly, we're not going to see a return of saber-toothed cats or giant bears. But we, or our children or grandchildren, may well have to deal with a Pliocene climate--much hotter, lacking most of the Northern Hemisphere's ice cover, and with rapidly rising sea levels.

Why aren't we already living in mid-Pliocene conditions? Simply because there hasn't been time for the full impact of the greenhouse gases we've already pumped into the atmosphere to warm the oceans and melt most of Earth's ice. Geochemist Gavin Foster, also at the University of Southampton explains:

... it takes a while for Earth’s climate to fully equilibrate (catch up) to higher CO2 levels and, because of human emissions, CO2 levels are still climbing. Our results give us an idea of what is likely in store once the system has reached equilibrium.

To get a sense of what things will be like when Earth has reached that Pliocene-like equilibrium, picture your favorite coastal city under 80 feet of water. According to recent research, coastal flooding could displace hundreds of millions of people and cost the global economy trillions of dollars by the end of this century if we don't get a grip on climate change now.

Keeling curve--atmospheric CO2 1960-2020

Credit: Scripps Research Insitute

Right now we're at 413 parts per million of atmospheric CO2, and rising, and the curve is getting steeper. We're running as fast as we can towards a very inhospitable past.

--REA

FUEL ON A FIRE--HOW CLIMATE CHANGE MADE HURRICANE HARVEY WORSE

Just a quick link to an important piece by climatologist Michael Mann detailing the ways in which global warming and climate change added destructive power to Hurricane/Tropical Storm Harvey:

https://www.theguardian.com/commentisfree/2017/aug/28/climate-change-hurricane-harvey-more-deadly

The factors Mann details include sea level rise (compounded by subsidence from oil drilling); warmer surface and deep waters in the Gulf which added to the energy/intensity of the storm, the storm surge it caused, and the amount of water it dumped on land; and the fact that it stalled over Texas, producing those all-time-record-breaking rainfall totals.

In the absence of meaningful action to control climate change, we're going to see a lot more of these "once-in-a-thousand-year" disasters.

One of thousands of rescues in the aftermath
of Hurricane/Tropical Storm Harvey
Credit: Dept. of Defense

NATURE SHOWING WIDESPREAD CHANGES FROM JUST ONE DEGREE OF WARMING--MORE TO COME

A few years ago I was backpacking in California's Sierra Nevada. Sitting by an alpine lake late in the afternoon, I noticed something interesting. On the hillsides rising up from the lake the stands of pine trees showed a striking pattern. On the lower slopes there were only the remains of dead trees--tall, scraggly skeletons with a few bare branches. A bit higher up the slope was populated by clusters of trees, not the age or height of the dead giants below, but a substantial, growing population. And above them were saplings, staking out still higher ground. "Look at that," I said to my hiking buddies, "the trees are migrating up the slope."

June Lake, Sierra Nevada Range/Credit: Don Graham

At the time, we were pretty sure that we had stumbled upon one, small, local impact of climate change, although of course we knew that what we were seeing could be explained in other ways, and that one case doesn't prove anything.

However, our intuition was probably right. A new study in the prestigious journal Science surveys multiple studies from around the world and finds that 82 percent of the vital biological functions they examined showed clear changes in response to the 1 degree C the Earth has warmed since the beginning of the industrial revolution.

"Genes are changing, species' physiology and physical features such as body size are changing, species are shifting their ranges and we see clear signs of entire ecosystems under stress, all in response to changes in climate on land and in the ocean," says wildlife ecologist Brett Scheffers, at the University of Florida.

Climate change impacts on ecological processes in marine, freshwater, and terrestrial ecosystems/Credit: Scheffers et al., Science, 11 November, 2016

The authors explain that the genetic, physical and population changes they documented represent crucial aspects of the healthy functioning of Earth's ecosystems, biological systems on which human well-being depends. These impacts varied from 60 percent for genetic changes to 100 percent for changes in species distribution. And, these wide-ranging impacts are happening sooner than many experts expected.

"Some people didn't expect this level of change for decades," said environmental researcher James Watson, at the University of Queensland, Australia. "The impacts of climate change are being felt with no ecosystem on Earth being spared."

It's important to recognize that these changes are not just abstractions of interest to scientists and nature lovers. They impact us all directly. The authors write:

Disruptions scale from the gene to the ecosystem and have documented consequences for people, including unpredictable fisheries and crop yields, loss of genetic diversity in wild crop varieties, and increasing impacts of pests and diseases. 

Since we're seeing these across-the-board changes sooner than expected, and with only one degree C of human-caused warming, it becomes all the more urgent to do everything we can to reduce CO2 and other greenhouse gases, and to move as quickly as possible to alternative energy sources such as solar, wind and hydro.

With the coming Trump administration threatening to do everything it can to reverse the progress towards climate-change mitigation that the US has made in recent years, we will have to look to the rest of the world to recognize the need to sustain a healthy and habitable planet, and act to preserve it.

AN APPLE A DAY KEEPS THE GREENHOUSE AT BAY

We've known for many years that raising animals for meat is an incredibly inefficient way to feed people. Meat production uses a huge amount of land, water and energy, and produces a huge amount of methane, a potent greenhouse gas, and other forms of pollution.

Grazing cattle/Credit: USDA

Now, for the first time, consumers can compare the environmental impact of different kinds of food.

Researchers at Lancaster University, in the UK, and RMIT University, in Melbourne, Australia, reviewed 369 studies concerning the global warming impact of the production and distribution of a wide variety of foods. To help consumers, they've summarized their findings in a simple table.

The gist of what they found is that meat from ruminants such as cattle and sheep has the worst impact on the climate. Worldwide, one kilogram (2.2 lbs.) of greenhouse gas emissions only yields 38 grams of beef (that's just .08 pounds). Pork was better, but far from ideal, with one kg of greenhouse gas production yielding 174 g (.38 lb.) of pork. Chicken was better still, with a 270 g (.6 lb.) production of chicken at the cost of 1 kg of greenhouse gases. Fish and eggs were in the same intermediate range.

However, the winners by far were in the veggie department. For example, 1 kg of greenhouse gas emissions came from the production of 1 kg (2.2 lbs.) of lentils or 2.6 kg (5.7 lb) of oats.

And, getting back to the title of this piece, you can produce and distribute 20 medium-sized apples (3.5 kg, 7.7 lb.) at the cost of 1 kg of greenhouse gas. By weight, that's a whopping 92 times better than beef. (Onions were an even better buy for the environment, but I figure that an onion a day would keep everyone away).

Now that 193 nations have signed the Paris Agreement, vowing to do their part to combat global climate change, one thing each of us can do is shift our diets away from meat and towards more fruits and vegetables. How hard can that be?

A child eating an apple/Credit: USDA