Are we in the middle of a sixth mass extinction?

Throughout Earth's history, there have been five great mass extinctions.  In each one, over 75% of all species disappeared within a million years.  New research, recently published in Nature, suggests that we may be in the midst of a sixth mass extinction, caused and/ or exacerbated by a variety of human activities, including:  hunting, overfishing, deforestation, the introduction of non-native species, the spreading of pathogens, and of course, global warming.

To determine whether a mass extinction is indeed in progress, scientists compared current rate of extinctions to historical, background extinction rates.  They determined that the current extinction rates for mammals, amphibians, birds, and reptiles, if calculated conservatlvely over the last 500 years, are well above normal.  They estimated that current rates of extinction are faster than, or as fast as, all of the rates that would have produced the past "Big Five" extinctions.

The researchers mention a variety of methods to estimate extinction rates and compare them.  One of the most commonly used ways to make this comparison is to estimate the number of extinctions per million species years (E/ MSY).  Background rates are estimated from fossil extinctions that took place in million-year time intervals.  For current rates of extinction, the proportion of species extinct in a short time interval (a couple of centuries) is extrapolated to predict what the rate would be over a million years.

The authors are quick to point out that measuring mass extinction is not an easy task.  There are a number of biases with both fossil data and modern species data that can make comparison difficult and oftentimes, uncertain.  However, they point out that even the most conservative analyses still provide evidence that a sixth mass extinction, is indeed, taking place.

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Sharinne Sukhnanand

These briefs are part of a weekly series of updates to the publication: Climate Change - Past, Present, and Future: A Very Short Guide.  The entire series can be found here.

Typewriters are to computers as cars are to: ___________________

We often write Climate Change 101 blog posts about efficiency, and I think that's great. Today's post takes a different tack, and instead raises questions about doing something else instead of doing something more efficiently. What does that mean?

Consider why someone might want to buy a Hummer, for example. Sure, it will get you from Point A to Point B. In the eyes of some, it gets you there in style. I suspect it's relatively comfortable too. There are certain conveniences provided by having any vehicle -- you don't have to travel on someone else's schedule. You don't have to worry about if a bus or subway stops near your starting and ending points. It gets you there faster than walking or biking and in a climate controlled environment.

There are certain inconveniences too. You have to pay for the thing, to insure it, to fill it with fuel, to maintain it, and to fix it when something breaks. You also have to park it. And it's got emissions, of course, and we know those change the chemical composition of the atmosphere which in turn changes the dynamics of the atmosphere.

Indeed, the climate-controlled environment that it provides for its passengers while en route contributes, just a little on the individual level, to the destabilization of the global climate (which is why I'm writing about it here). Scale it up to the hundreds of millions of vehicle owners the world around, and it's no longer just a little. (See previous posts: Making the Case as Simply as I Can,  How can the CO2 released weigh more than the gasoline I started with?, and Interesting Conversations Happen on Facebook for more on how emissions scale up to major problems).

Many of us, myself included, think we want a car. I'm suggesting that we step back from that and consider what services it is we want from cars, and think about if we can get equal or superior benefits in another way at a comparable or lower economic cost while lowering environmental costs.

I don't really want a car. I want to get from Point A to Point B with reasonable convenience, in comfort, and, I admit, I want to get there in some sort of style. Aspects of my family's style are conveyed by our ten year old Prius with its environmentally themed bumper stickers. I also don't want my transportation to cost too much -- for either me or for the environment.

Where I'm going with this might be summarized by an SAT-style analogy question:

Typewriters are to computers as cars are to: ___________*

Making cars more efficient is clearly important, and I'm really glad smart people are working on it. But what I'm wondering is: Can we make something more efficient than (and just as desirable as) cars? Sometimes fundamentally new technologies push away the old. A jet is not a re-engineered canal boat or train.

And, it's not always about more efficient ways of doing the same thing. Trains, planes and automobiles are all instruments for transporting people and goods from Point A to Point B. Part of the idea is also developing ways of meeting the needs and wants achieved by travel without the travel.

I mostly Skype to work. And it allows me to work all over the country and the world without doing nearly as much travel as this sentence implies (though I still do way more travel then I'm comfortable with from an environmental perspective). But it's a step in the right direction, and the technologies are improving at a blazing pace.

It's not just about changing technologies, either. I hope my next car is a rental. Or a car-share. Or improved mass-transit. None of those changes require new technologies, they just require people (my family) to do things differently. I'm part of a two-car family, but at least one of those cars is almost always parked in the driveway. If it was just a little more convenient for me to access a car sharing program or rental car, we'd be able to move to being a one-car family with the primary change in lifestyle being more money in our bank account.

Recognizing that we need a much longer blank line, how will you complete the analogy?

Don Duggan-Haas


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*Some of you may recognize this as a favorite question stem of mine. Change "cars" to something else, like "schools" and you can push your brain in interesting directions. And I think you should.

Should we believe the scientists?

My friend, English teacher, and inspirer of blog entries, Dina, recently asked me if I'd seen a couple of articles about problems of scientific studies. The articles in question are The Truth Wears Off Is there something wrong with the scientific method? by Jonah Lehrer, which appeared in The New Yorker and Lies, Damned Lies, and Medical Science by David H. Freedman, which appeared in The Atlantic.


A bit of background, and a plug to join our group:
She raised the question in context to an ongoing discussion about teaching climate change that I facilitate for a small group of educators. We meet monthly and share resources and try and work through ways to improve our approach to instruction around issues of climate change. Our meetings are online, via Skype and our next meeting is April 14 at 8:15 pm EDT.

For this coming call, we'll be talking about Greg Craven's book, What's the Worst That Could Happen?  The book holds an important message, but Craven's writing style is that of a goofy science teacher. That's off-putting to some, but it happens to resonate with me. And, again, the central message of the book is really important. Through the book, Craven also develops a pair of nice conceptual tools for looking at the question of the title. One of those is a "credibility spectrum" that helps you rate different sources of information.

I talked about some of this at last month's National Science Teachers' Association Annual Meeting, and you can download handouts including the credibility spectrum. It's in two parts -- here and here. You can also see the presentation slides here, but it's not needed to understand the rest of this post.

That context is important for understanding Dina's question.

And, if you're interested in joining in our conversation on 4/14, drop me a note. It's a small part of a larger project called Climate Lifelines. The target population is high school teachers, but anyone teaching about climate change is welcome to join.

Now, back to Dina's questions
Here's what she said after sharing the article links:

Thoughts?

They make me question Craven's credibility scale. As does the increasing prevalence of science that is being funded by corporations with investment in a certain answer. 

I am not to the point yet where I am a climate change denier. But I do wonder about the intensity of the predictions involved. 

For example. (This is not terribly scientific, but anyway). The incredible ability of ecosystems to repair themselves is well documented. So let us say we do run out of fossil fuel before we reach some kind of climatic tipping point (which as far as I know, is a distinct possibility)-- to the point where it becomes a de facto worldwide carbon-zero reduction program. I don't hear much, if anything, about the possible *positive* impact this may have on climate change.

Here's what I wrote back:

They don't do much to sway me away from thinking that global warming is human caused and I was already leery of putting too much stock in individual studies. I've spent enough time with academics to know that they're human and the process reduces errors but doesn't eliminate them. 

I also think the examples used in the two papers are of a different sort than the things that make the general conclusions related to human-induced climate change durable. They're both simpler than the big picture and more complex than the fundamental physics and chemistry. 

It's been observed probably thousands of times in the lab that if you add carbon dioxide to air and shine light through it to warm up materials within the contained system that it will heat up more than a similar apparatus with less carbon dioxide in it. That's simple and it would be pretty stunning if it started working differently. The examples used in the paper all deal with stuff more complicated than that. So, that's where the climate change bit is simpler than these examples.

It's more complex in the huge range of observations, studies and predictions based on the idea that changing atmospheric chemistry in the way we're doing seem to fit together so very well. I guess that's both complex (at the level of all the different aspects of the Earth system) and simple (in that the outcomes seem to match (or exceed) the predictions). 

I think even if it raises questions about Craven's credibility spectrum, it mostly just makes more room at the top. I don't see what's more reliable than the scientific consensus. 

And, it is true that, if you don't cross certain tipping points (like extinction) ecosystems can bounce back pretty impressively. Of course, there's no bouncing back from extinction.

As for running out of fossil fuel before reaching climate tipping points, I'm personally worried that we're awfully close to the tipping point if we've not reached it already, and we're not on the cusp of running out of fossil fuels. They are, however, running out of the low hanging fruit of fossil fuels. Technologies, like horizontal drilling coupled with hydraulic fracturing, however effectively lower that fossil fuel fruit pretty regularly.

Hmmm... Did I just write most of an overdue blog post? What do you think?

Don