Greetings from the Climate Strike

 This photo is from Greta Thunberg's Facebook page.

This past Friday, September 20, 2019, a youth-led climate strike took place in cities across the world.  Several million people globally, including up to a quarter million people (according to organizer estimates) in New York City, took to the streets to demand that world leaders respond to climate change and global warming with the urgency that science indicates is necessary.  As one of the massive army in New York, I was impressed and inspired by the energy of the protesters and their optimism in their own ability to make change.  But as an atmospheric scientist who has been studying the physics of climate for longer than most of my fellow protesters have been alive, I felt a tinge of sadness that it had come to this.

As sixteen-year-old Swedish activist Greta Thunberg pointed out in her speech to the United Nations on September 23, "For more than 30 years, the science has been crystal clear.”  The climate science community have gathered quite a bit more data since Dr. James Hansen’s 1988 visit to the U. S. Senate made “global warming” a household term, but the data have reinforced the conclusions, not altered them.  The Earth is getting warmer, at a rate which cannot be explained by any known natural cycles.  It can be largely explained, however, by the rapid, steady increase in atmospheric concentrations of carbon dioxide, instigated by the burning of coal and hydrocarbons for energy and aggravated by the loss of forests which serve as the Earth’s primary natural “sink” for the gas.  This is because carbon dioxide absorbs the kind of infrared radiation that the Earth emits, so that the energy contained in that radiation stays in the atmosphere and does not escape into space.  This warming will have consequences, including rising sea levels, stronger storms, and longer and more deadly heat waves.  And the cost of accepting these consequences will be far greater than the cost of preventing them would be.  None of this is new.  None of this is even up for debate on the grounds of reasonable doubt.  And yet, for as long as I've studied atmospheric science, I’ve felt that I was banging my head on a brick wall every time the subject came up in conversation.  I’m not sure that I’ve changed the mind of even one of my skeptical friends and relatives.  And people who have no interest in even acknowledging the existence of global warming, much less doing anything about it, continue to win far too many elections.  But young people have begun to realize that the consequences of global warming will affect them more than they will affect people my age, and they have started listening.  As Thunburg told Congress last week, “I don't want you to listen to me.  I want you to listen to the scientists.”  It would have been self-defeating, on many levels, for me NOT to go and lend my support.

The quote on the poster is from Dr. Seuss's "The Lorax"

I decided to wear a T-shirt I have that says “Ask me a question, I am a scientist.”  I got that shirt volunteering at the Long Island Mini Maker Faire in Port Jefferson, NY this past June.  As I said when I started this blog, one very useful thing we can do as individuals to combat global warming is simply to talk about it, in order to raise awareness and improve understanding.  I figured that shirt would be a good conversation starter.  And indeed, both before and after the march, I had a number of people come up and ask me questions.  Most of the questions were some variation of, “How screwed are we?”  That's not an easy question to answer, because how the Earth looks a century or two from now will depend quite a bit on our actions in the meantime.  The present politically-established benchmarks are not adequate to prevent massive long-term damage.  The Paris Agreement talks about limiting warming to 1.5°C above pre-Industrial levels. But the last time the Earth’s temperatures were as warm as they are now (about 1ºC above pre-Industrial level) for a significant length of time, sea levels were 20 to 30 feet higher.  And the last time levels of carbon dioxide in the atmosphere were as high as they are now, sea levels were 50 to 60 feet higher.  That's the world our descendants would inherit if the current temperature or carbon dioxide level is maintained for a century and beyond — but of course we’re nowhere near leveling off anything.  The good news is that it doesn't have to be that way.  Clean energy is cheaper right now than most people realize, and the technology is improving and will continue to improve if politics allow it.  But, consequences are happening right now.  Sea levels have risen about 8 inches on average globally since the late 1800s, and about a foot in New York City.  That foot mattered when Superstorm Sandy hit my area in 2012.  And those extra inches mattered in the Bahamas this past month when Hurricane Dorian hit.  So did the increasing intensity of hurricanes — the Atlantic used to see a category 5 hurricane once every three years on average, but this is the fourth straight year we have seen one.  As of September 23, 53 people are confirmed dead because of Dorian, but over 1000 are still missing.  And the fierce heatwave in Europe this summer killed 1500 people in France alone.  It didn’t have to be that many, and yet that won’t be the worst heatwave that young or even middle-aged people in France will live through.  The rate of sea level rise has begun to accelerate, and is projected to accelerate further.  It may take a while to level off, even if we do start to act decisively; a just-published paper by a former colleague of mine concluded that it would take twenty years to slow down (much less stop) the rate of temperature increase even with a quick phaseout of fossil fuels.  And temperatures will have to go down before sea level rise can be reversed.  So lives hang in the balance right now, and the number of people killed, or displaced, or pushed from the category of people who “have” to people who “have lost,” will grow and grow.  Unless.

Taken from this article.

From Greta Thunberg's Facebook page.

Here on Long Island where I live, I have friends who write and sing children’s music.  My favorite song of theirs, titled “One Drop in a Bucket,” talks about how one seemingly small action can cascade into something much larger.  I wonder if Greta Thunberg, when she first showed up outside the Swedish Parliament on a Friday last August carrying her now-iconic poster, had any idea that millions of children would eventually join her.  Or that her simple action would be chapter one in a Tolkienesque quest that continues for her thirteen months later.  But that’s what happened.  For the first time in my professional life, I know that there is a large group of people who take the issue of climate change and global warming as seriously as it needs to be taken.  And to those people I can only say, “thank you.”  I’m sorry it has been left to your generation, and I take some responsibility for the fact that we have not done enough, nor have we really tried.  But I’m still here, and I promise to keep banging my head on as many brick walls as I come to, for as long as it takes.

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Hope for Renewables

One of the biggest obstacles that renewable energy needs to overcome, in order to provide the lion’s share of the world’s electricity needs, is that it delivers power intermittently.  Solar and wind do not generally provide maximum power at the times that power is needed most, nor can they be counted on to provide power steadily throughout the course of a full day.  And yet the share of renewables in the energy market is growing, largely to this point for economic reasons.  The most recent report on the levelized cost of energy by the investment banking firm Lazard has the price of new utility-scale solar ranging from $36-46 per megawatt-hour (MWh) of energy produced, while onshore wind varies from $26-56 per MWh.  Compare this to the $41-74 per MWh for new natural gas plants, and especially the $60-$143 per MWh for new coal, and the appeal of renewables becomes obvious even before taking environmental factors into account.  According to a recent report published by the Federal Energy Regulatory Commission, the combined capacity of renewables (including hydroelectric, biomass, and geothermal) eclipsed that of coal in this country for the first time in April 2019.  Solar and wind do not yet control a big share of the energy market.  But that will change, perhaps sooner than you think, if the cost of wind and utility-scale solar continue to trend downward.  Plus, transitioning to a clean energy economy will need to be done with more urgency if the United States and the other nations of the world wish to meet their commitments to the Paris Agreement — assuming that those commitments are even sufficient to stop the effects of global warming from causing significant damage and upheaval on a global scale.  

There are basically three ways to address the intermittency issue if the goal is to reduce carbon dioxide emissions in the power generation sector.  One option is to maintain a significant supply of natural gas to run during times that solar and wind are not generating sufficient power.  But even though natural gas is relatively cheap and emits about half as much carbon dioxide per energy released than coal does, it is not likely that the Paris goals can be reached if emissions in the electricity sector remain substantial.  (Keep in mind that clean transportation presently appears to be a more distant objective that clean electrical power is.)  Another possibility is the continued use of nuclear power, including the construction of new nuclear plants.  Nuclear power does not produce greenhouse emissions, but it is beset by economic issues — according to Lazard, the cost of a new nuclear plants would range from $112-189 per MWh.  Ironically, nuclear plants are actually the cheapest type of power plant to operate once the cost of construction has been fully accounted for (only $28 per MWh, compared to $36 per MWh for coal), which means the bulk of their cost comes from their construction.  According to a recent report by the Union of Concerned Scientists, a lot of existing nuclear power plants struggle to achieve cost-competitiveness largely because the companies who operate them are still paying off the construction cost.  The third option is to have renewables produce excess energy at the times of maximum power generation, and then store this excess in batteries.  This option often gets downplayed because it's still fairly expensive; a Bloomberg report from this spring set the levelized cost of battery storage at $189 per MWh in the spring of 2019.  But that price is 35% lower than it was in the spring of 2018, and there are markets right now where renewables with battery storage are cost-competitive, even without subsidies.  Furthermore, a 2018 report from the World Economic Forum suggested that by 2028, the cost of renewables plus battery could be lower than the cost of gas “peakers” in the grid.  And on July 1, Forbes magazine reported on a deal struck by Los Angeles Power and Water to create the largest and cheapest solar-plus-battery project in the world.  The solar power will be delivered at roughly 2 cents per kilowatt-hour ($20 per MWh), with an additional cost of only 1.3 cents per kilowatt-hour ($13 per MWh) for the battery storage.  This combination comes in below typical cost for both natural gas and nuclear power, and it sets the price bar for renewables plus storage that much lower.  It's tough to guess how profitable this plant will be in the long run, but it indicates considerable optimism in the direction the price of renewables with battery storage is going.

In an ideal world, we would collectively aspire to reduce carbon dioxide emissions in electricity generation as quickly as possible.  I’ve discussed a bunch of the reasons for that here on this blog, and continuing to debate what scientists have accepted for over forty years belies the urgency needed to tackle the problem.  People do have a right to be concerned that aggressive reductions will create economic setbacks that will ultimately do more harm than good, but evidence for that being the outcome does not actually exist.  Instead, the Fourth National Climate Assessment of the U. S. Global Change Research Program concluded that limiting global warming to 1.5ºC above pre-Industrial levels as opposed to 2.0ºC would save the American economy half a trillion dollars annually. And the Office of Management and Budget under the Obama administration estimated the economic damage due to global warming, simply in terms of lost federal revenue, could range from $340 billion to $690 billion annually if the status quo in the energy sector continues to hold and global temperatures rise to 4ºC above pre-Industrial levels..  But economics can certainly influence the direction that greening our energy sector takes.  Nuclear power does not leave a carbon footprint, but the cost of constructing new plants remains prohibitive and is not likely to come down.  The cost of battery storage is generally higher for now, but it is trending in the right direction, there is some justification for optimism long-term, and one present development suggests that the cost decline is occurring at a faster rate than projections from last fall and even this spring were suggesting.  And in the meantime, new solar and wind farms are cheaper in most places than new coal and gas plants are; in fact, there are already places in this country where it would save money right now to replace an operational coal plant with renewables.  This doesn’t mean that a major shift to renewables will be easy; in fact, a report out just this week suggests that investment in renewables is not rising but declining.  Present economics does not justify this reticence, though, and environmental concerns clearly demand moving strongly forward.

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Remembering Wally Broecker

Dr. Wallace Broecker, a Columbia University geophysicist and climate scientist, passed away this week at the age of 87.  He served as a professor at Columbia for over half a century and published over five-hundred papers in the field.  Broecker is best known, though, for the 1975 paper he published in Science called “Climate Change: Are We on the Brink of a Pronounced Global Warming?”  This paper is significant not simply for the fact that it inserted the term “global warming” into the middle of discussions of the Earth’s climate, first with scientists and then eventually with the public at large, but also because it largely resolved the debate going on in the climate science community about what was happening to the Earth’s climate and what the ultimate cause of that was.

Scientists had been aware, at least in an abstract sense, that carbon dioxide was capable of warming the atmosphere and that levels of it in the atmosphere were increasing  since the early part of the twentieth century.  However, it wasn't until 1958 that amounts of carbon dioxide in the atmosphere were first quantified.  The primary instrument to do this was set up on the summit of Mauna Loa in Hawaii by a scientist named Charles Keeling.  It became clear from Keeling’s data by the mid-1960s that CO2 levels were rising sharply, and that the rate of increase was accelerating.   Global temperature records were sufficiently well-established at that point in time for scientists to know that the planet on a whole had been cooling for the previous three decades, however.  Reconciling the rising CO2 levels and the greenhouse effect with cooling temperatures proved to be a challenge.  In fact, a paper published by two scientists from NASA/GISS in 1971 suggested that the cooling effect of aerosols was overwhelming the warming effect of carbon dioxide, and that humanity was running the risk of plunging the planet into a new Ice Age.  That paper turned out to be flawed, but a new scientific technique revealed that the cooling at the time was primarily the result not of human activity but a natural cycle. Ice and sediment cores were being used to estimate global temperatures in the recent and distant geologic past.  An eighty-year cycle of global warming and cooling found in this data could explain the cooling between the 1930s and the 1960s better than increases in global aerosol amounts could.

This is where Broecker’s famous 1975 paper comes in.  Using a computer model, Broecker was able to show that the natural cycle observed in the sediment cores, superimposed with the warming influence of carbon dioxide, could explain what had been observed in the temperature record up to that point.  But the model did not stop in 1975.  It also predicted that, as the cooling cycle was about to reverse itself and the warming effect of CO2 was strengthening steadily, a sharp and clearly discernible global temperature increase was imminent.  “Once this happens,” Broecker wrote in the abstract, the exponential rise in the atmospheric carbon dioxide content will tend to become a significant factor and by early in the next century will have driven the mean planetary temperature beyond the limits experienced during the last 1000 years.”  That actually wound up happening in the late 1990s, but it had become evident by the early 1980s that Broecker’s predictions were coming true.  As a result, the consequences of human activity on the Earth's climate became very clear to nearly the entire climate science community.

I only met Wally Broecker once myself.  He worked at Columbia, but he was mainly based at the Lamont-Doherty Earth Observatory in Palisades, NY and didn't come down to the Manhattan campus that often.  As my major was applied physics rather than earth science, I didn't go up to Lamont very often, either.  When I did meet him, at a talk he gave at GISS in 1996, I found him to be a very warm, friendly, and outgoing person with an accessible and approachable personality.  I was new to GISS at the time, but it was clear that everybody in the room looked up to him, and that was good enough for me.  He had a remarkable life and career, and while he may no longer be with us, his work remains an essential part of a critically important science.

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