December 2015’s crazy weather

I’m in Oregon, where December has broken rainfall records east of the Cascades, and the Cascades themselves are deep in snow. I got to see some of it up by Mt. Hood yesterday on a Christmas Day family cross-country ski outing.


Though that was beautiful, I’m still sad to be missing the record-breaking warmth back east. (I like warm weather; it’s not an accident that most of my research over my career to date has been about tropical meteorology.) To help myself experience it vicariously, I wrote an op-ed piece for CNN about what the probable causes are. It has even been translated into Spanish.

Urgency and Uncertainty in Rolling Stone

Eric Holthaus has a recent piece in Rolling Stone enitled “The Point of No Return: Climate Change Nightmares Are Already Here.” The subtitle is “The worst predicted impacts of climate change are starting to happen — and much faster than climate scientists expected.”

It’s a good article. But it highlights the difficulty of talking about current extreme weather events and their relation to human-induced climate change. On the one hand, the essential message of the piece is to communicate urgency on climate and need for action. This is right and appropriate. And sentence by sentence, the individual statements about specific weather and climate phenomena are accurate (at least those where I have adequate expertise to make an evaluation).

On the other hand, the piece implicitly attributes a lot of individual weather and climate events – all of those it mentions, really, which is a long list – to human induced climate change. Some of those attributions are justified, but others aren’t.

In the cases where the attribution isn’t justified, Holthaus doesn’t explicitly make it, not line-by-line in the sentences talking about those events. I couldn’t find anything outright wrong at that level. The piece was, clearly, researched and written quite carefully and with deep respect for the science. But the attribution is there implicitly, through the piece’s headline, its subtitle, and its overall framing.

I’ve added some annotations at the site Climate Feedback (my annotations and others’ on this piece are not visible yet, as far as I can tell; soon, I think), a new site designed for scientists to evaluate the science content in popular articles on climate. Two of my comments are about Holthaus’ discussion of the ongoing El Niño and positive phase of the Pacific Decadal Oscillation. These two are enough to make the point I’m interested in here.

These two climate phenomena, manifest by slow changes in the sea surface temperature in various parts of the Pacific ocean are indeed having major impacts, as described well in the article. But most climate scientists consider these phenomena to be essentially natural. We can’t be certain that the current instances of El Niño and the Pacific Decadal Oscillation aren’t in any way connected to human induced climate change, but there is no convincing evidence of such a connection, to my knowledge. Holthaus doesn’t say there is one, but to my eye it’s clearly implied. The title and subtitle, as well as the overall framing of the piece, say that it’s a list of impacts of “climate change” – which presumably most will understand to mean “human induced climate change”.

I’m being critical on this issue because it’s one I struggle with myself, and because Holthaus is a thoughtful, serious and committed writer on climate, one who actively seeks criticism from scientists (I understand that he asked Climate Feedback to evaluate his piece). And because while I read the piece as making some implied claims that are outside what science can justify, I agree completely with its bottom line, and appreciate the force with which it comes across.

Human-induced climate change is real, is a grave threat to human society, and is already having significant impacts now. Some of the events Holthaus describes almost certainly do have some imprint of human influence: heat waves and ocean acidification, for example. And natural and human influences can’t be completely untangled. While the heat, drought and wildfire in the west now are likely caused in large part by natural variations in the Pacific sea surface temperature (El Nino and Pacific Decadal Oscillation), greenhouse gas warming adds extra heat, making the impacts worse.

And regardless of the causes of individual extreme weather and climate events now, the disasters they cause still tell us something about our vulnerabilities, and that is relevant to the longer-term climate change question. The human influence will grow larger in the future, as warming proceeds. It will eventually make some kinds of extreme events significantly, detectably more frequent or more intense, even if we can’t clearly detect that influence in individual events of that type happening now. (Tropical cyclones are a good example of this.) The current events can rightly be seen as harbingers, if nothing else.

Holthaus writes quite a bit about the recent paper by James Hansen and colleagues, which warns that sea level rise may occur much sooner and more severely than most of us had thought. This paper is controversial, and not yet even through peer review. But in my view it deserves the coverage it gets, here and elsewhere – its predictions may or may not be right, but it seems pretty clear that we can’t rule them out. Contrary to denialist lines of argument, the uncertainties in climate projections should make us more worried, not less.

What if Holthaus had made a more concerted effort to avoid any implication of human influence on events to which it wasn’t justified? In a piece with the title and subtitle that this one has, the simplest way to do that would have been not to write about those events at all. That would have meant leaving out some of the most serious and visible disasters going on right now in the US, where the main readership for this piece presumably is. Alternatively, the piece could have had a different title and subtitle (my guess is that these were written by an editor rather than by Holthaus himself), one that communicated that the piece was about events of both natural and human origins. Either way, would the sense of urgency have been diluted?

Professional scientists are sometimes criticized for under-communicating the urgency and reality of climate change, especialy when we talk about current extreme events. This criticism is often fair in my view. We talk so much about the uncertainties that we leave nonscientist audiences with the feeling that we don’t know anything. We do this, I think, because we are used to talking to each other. Being clear about uncertainties is an inherent part of scientific practice. Also, our colleagues already share our knowledge and understanding of the big picture on climate change – the consensus is real – so we don’t feel a need to restate that. We fail to recognize that that underlying knowledge is not shared outside our professional circles, and that it’s often appropriate to emphasize what we do know more than what we don’t.

Journalists, on the other hand, are often criticized by scientists (and others) for overstating the connection of extreme events to climate change by glossing over uncertainties – as I have done here, in my first few paragraphs above. This is also often fair, and as with scientists, similarly traceable to the daily realities of their jobs. Journalists are under great pressure to make it current, make it exciting, keep it simple. It’s easy to see how that leads to a little exaggeration and overstatement, whether by implication or outright.

If there’s a perfect solution I don’t know it. I’m glad that writers like Holthaus (and many other good ones) are grappling with the science and doing their best to keep it accurate while still getting the essential message on climate into the popular press. I don’t love everything about this Rolling Stone piece but I think we need more like it anyway.

Full disclosure: Eric Holthaus is an alumnus of Columbia University, where I teach, though I didn’t teach him when he was here and haven’t met him in person to my knowledge. He has interviewed me a couple of times for other pieces he has written, though not for this one in Rolling Stone. He wrote a very kind review of my book when it came out last fall.

Spring ahead

As I write the temperature in NYC is approaching 80F. Most trees, though, are still leafless.

It’s not unusual to have days like this here around this time of year, when the temperature races ahead of the foliage as the sun rapidly climbs higher in the sky. This year the leaves and flowers are coming in late, making a day like today almost inevitable.

I haven’t been able to find a quantitative analysis online of just how late this year’s leafout is, relative to long-term averages, but the cherry blossoms in Washington, DC seem to have peaked about a week late, and my guess is that we’re running at least that far behind schedule here in New York after the harsh winter we had.

The long-term trend, on the other hand, is towards earlier blooming as the climate warms. But as with everything else about late winter and early spring, you wouldn’t have known that from this year in the northeast.

I went for a walk this afternoon along the Hudson River promenade, and it was a good few degrees cooler down by the water. The transition seasons are when the temperature contrast between land and large bodies of water peaks, as the large thermal inertia of the water remembers the season past while the land responds quickly to the sun.

Back in March, when it seemed like winter would never end, I found it comforting to keep reminding myself that the seasonal cycle is inexorable – nothing stops the earth’s orbit.

Sometimes in climate change debates, you hear someone ask “If meteorologists can’t predict the weather two weeks in advance, how can they predict it 50 or 100 years in advance?” The basic answer is that we aren’t predicting weather far in the future, only climate. The two are different. The seasonal cycle provides a useful way to make this less abstract.

I can’t predict exactly what the weather will be on July 4th, but I can predict with unshakeable confidence that it will be a lot warmer than it was in February or March. In fact, I can predict that summer will be warmer than winter every year, forever. That is a climate forecast. The seasons change because of changes in the radiation incoming at the top of the atmosphere, and that’s exactly the same reason that greenhouse gases are inducing a long-term warming trend.

Sure, there are differences. The summer-winter changes in insolation are much larger than those due to human-induced greenhouse gas changes; the seasonal change is mainly in the visible part of the electromagnetic spectrum while the greenhouse gas forcing is in the infrared; the greenhouse gas influence is global while the seasonal changes are opposite in the two hemispheres; and we have a much longer history of observing the seasonal changes, so a more or less correct prediction can be made empirically, without any physical understanding. But really, the basics are quite similar. So anyone who thinks a climate forecast can’t be done can benefit from thinking about what is behind the changes happening at this time of year.

Paleo trash and unfrozen cavemen

Temperatures in NYC have finally risen persistently above freezing, and the ice and snow are starting to melt. In NYC one of the consequences of this is that all the garbage that was buried by the snow comes to the surface. The streets haven’t really been cleaned in weeks to months, and they are a mess.

It reminds me a bit of other things revealed by melting ice. Like Captain America in the movie… or, ok, if we want to be more real life-based, like Oetzi, the “iceman”, found in 1991 in the Alps between Austria and Italy. He was frozen 5000 years ago, and then unfrozen as the glacier he was in melted due to whatever combination of natural climate variability and anthropogenic warming.

So now today, we have scenes like this:

paleo trash march 2015

A little less scientifically important than Oetzi, but still, recent history (of a New York City sidewalk) preserved in ice and then revealed.

Of course, the most important artistic comment on this particular phenomenon is this.

US-China climate deal

I have an op-ed piece on CNN today about the new climate agreement between the US and China. The full piece is here, and the first three paragraphs below.

The agreement between President Obama and President Xi of China to reduce greenhouse gas emissions is the most important advance in the several decades-long history of international climate negotiations. It has been greeted with rage by those in Congress whose positions on the science are denialist or evasive (“I am not a scientist”). Their criticisms are specious and predictable.

But while most climate scientists I know are still sharing a period of joy following its announcement, some substantive criticisms of the agreement have also been raised. I want to address two of them here.

One is that the agreement doesn’t do enough to solve the problem of global warming. The other is that it doesn’t promise anything that wasn’t likely to happen anyway. Both of these criticisms have some truth, but neither diminishes the importance of what Presidents Obama and Xi have achieved.

Continue to full piece…