Climate Change Blogs

Carbon Dioxide Hits a New Peak this Spring: 404 ppm

Published: Abril 21, 2015
Weekly carbon dioxide measurements from the pristine air atop Hawaii’s Mauna Loa have just topped another predictable yet worrisome milestone: 404 parts per million. The actual preliminary value reported by NOAA for last week (April 12–18) was 404.02 ppm. By all evidence, we now have the largest amount of CO2 present in Earth’s atmosphere for at least the last 800,000 years, and probably several million. The most prevalent of the human-produced greenhouse gases, carbon dioxide has been measured regularly by scientists at Mauna Loa since 1958. The gas is also measured at other sites around the world, but the Mauna Loa dataset is the most widely tracked index of global trends because of its uninterrupted 57-year length.

The weekly CO2 readings at Mauna Loa will crest over the next couple of months, making a run at 405 ppm before the annual seasonal decline begins (see below). Eyeballing the multiyear trend shown in Figures 1 and 2, it’s a fair guess that the final time we see a weekly value below 400 ppm will be somewhere toward the end of 2017, perhaps a year sooner or later. From that point on, we’re unlikely to again see a week below 400 ppm for many years—probably centuries, if not millennia—because of the ever-increasing accumulation of atmospheric CO2 produced by burning fossil fuels.


Figure 1. The last two years of daily, weekly, and monthly averages for carbon dioxide concentration measured by the Scripps Institution of Oceanography atop Mauna Loa, Hawaii. NOAA operates a parallel measurement program at Mauna Loa. Image credit: Scripps/The Keeling Curve.

What’s in a curve?
One of the most renowned images in climate science is the Keeling curve (see Figure 2), generated from the Mauna Loa data. This trace is famous for its inexorable year-to-year increase in CO2, as well as the seasonal rise and fall embedded in the graph’s sawtoothed pattern, a trait that became evident as early as 1960.


Figure 2. The Keeling Curve, 1958-present. Image credit: Scripps/The Keeling Curve.

Because the Northern Hemisphere has far more plant-friendly land mass than the Southern Hemisphere, it has an oversized impact on the global CO2 pattern. The result is a net global addition of carbon dioxide to the air as northern plants decompose, from around October till May, then a net removal as northern vegetation surges from roughly June through September. These natural seasonal spikes are about twice as large as the amount added each year by fossil-fuel burning, which has recently averaged just over 2 ppm per year. Unlike the human contribution, though, the seasonal spikes cancel each other out over time. After removing the seasonal cycle from the long-term record, we end up with a steady increase that topped 400 ppm for the first time in March, according to NOAA.

Close inspection of the the Keeling curve reveals some embedded nuance apart from the obvious seasonal cycle and the long-term rise. Figure 3 (below) shows how the percentage increase in carbon dioxide concentration at Mauna Loa varies from year to year. These bumps and dips arise from both natural and human factors.


Figure 3. The annually averaged growth rate of carbon dioxide, in parts per million, as measured at in the atmosphere at Mauna Loa. Horizontal black lines show the growth rate for each decade from the 1960s to 2000s. Image credit: NOAA Earth System Laboratory.

In a typical year, about 57% of the CO2 emissions put into the atmosphere by human activity remain in the air, showing up in the long-term measurements at Mauna Loa and elsewhere. The other 43% is removed by plants, soil, and oceans. These percentages have held remarkably steady over the long haul, but they can also vary markedly from year to year. El Niño, for example, tends to pinch off the cold equatorial upwelling that normally sends large amounts of CO2 into the air, thus causing a temporary drop in the overall global rate of increase.

The human contribution from fossil fuel also varies from year to year. Global emissions of carbon dioxide actually dropped slightly during the recession years of 1992 and 2009. Likewise, CO2 emissions tend to increase at a faster clip when the global economy is especially robust. Policymakers have long taken this connection between emissions and economic activity for granted. Many were surprised, then, when global CO2 emissions in 2013 came in essentially flat even though the world’s gross domestic product had risen by about 3%. This could be a one-year fluke--scientists and policy experts have been debating this point--but it’s also a hopeful sign that our global economic engine just might be able to run on less coal, oil, and gas while still performing well.

The long view
How high the concentrations get in this century and beyond will depend in large part on what measures the global community takes to restrict carbon missions, including any agreements hammered out at the crucial UN climate meeting in Paris this December. Technology is a huge player, of course: wind and solar power, hydropower, and nuclear power are all close to carbon-neutral when compared to fossil fuels. But unless a price is set on carbon through some globally accepted process, there will be powerful market incentives for a growing world to use as much of our existing reserves of oil, coal, and natural gas as possible. And a key insight vividly highlighted by author and activist Bill McKibben remains: Earth holds several times more fossil fuel than needed to push global warming above the 2°C benchmark widely accepted as a target to minimize the odds of major climatic disruption.

Bob Henson


Figure 4. Atmospheric carbon dioxide concentrations derived from ice cores (prior to 1958) and Mauna Loa data (from 1958 onward) show the rises and falls associated with several ice ages and the dramatic spike of the last 100 years. Image credit: Scripps/The Keeling Curve.
Categories:Climate Change

It’s April, Time to Finally Think About 2015

Published: Abril 7, 2015
It’s April, Time to Finally Think About 2015

April, winter semester at Michigan comes to an end. I’ve been re-grouping myself on the blogging front, thinking about where to pay attention for this year. I'm back.

My climate-change problem-solving class, this term, has had one excellent guest lecturer after another. With the help of my colleague in the Ross School of Business, Andy Hoffman, we decided to experiment with my class to see if we could create something unique and potentially valuable. Our goal is to develop a new type of graduate curriculum, with a focus on, for example, climate change, but with a more formal systems approach to how does climate change fit into the world as a whole. We intend to create a new portfolio of curricular and co-curricular activities which can be used by professional Master’s programs across the university to incorporate sustainability into their programs. The centerpieces of this program are focused on interdisciplinary processes and engaged with real world partners and problems.

Andy Hoffman has a new book How Culture Shapes the Climate Change Debate. Here’s a nice review from the Union of Concerned Scientists.

My class has always been focused on participatory, cross-disciplinary problem solving, but we worked to integrate more strongly around some themes. We are especially interested in training students who can, perhaps, hit the ground in corporations, governments, non-profits, communities, all – hit the ground with skills on using climate-change knowledge and data in design, planning and management.

Towards the goals of my class, I have formalized, which might mean to make even more tedious, my approaches to structured problem solving. Not completely through it all, yet, but I am collecting the slides and some annotated, recorded lectures at this link.

I will use some of the guest lectures to bring new material to the blog. There has been more, than in previous versions, of a focus on design. We all know that we in the U.S., in fact much of the world, are stunningly inefficient in our use of resources. I have been especially impressed to see the value of design that links function, resource use and use of resource waste. Here is a interesting link to visionary design Infra Eco Logi Urbanism.

Last year, I spent several blogs following the El Niño prediction and its representation in the press. Also spent time being preachy about our fascination with monthly temperature records. This year we still flirt with a small El Niño, and people are talking, mostly with calm, that this year, 2015, is likely to break yet another record. It will not take much warming of the eastern Pacific to assure a very warm year.

This year, I am planning to develop a thread of blogs leading up to the Conference of the Parties in Paris. The University of Michigan is planning to send a delegation, and we will be coaching up some students and faculty for this event. Compared to my normal state of mind, I am more optimistic than previously that Paris will lead to something more substantive than previous international meetings. It might not be possible to develop a whole United Nations wide agreement, but the major players in the world are starting to see strategic advantage and possibility to addressing climate change. Not to mention, of course, the direct consequences of climate change we will have to deal with.

Part of run up to the Conference of the Parties will be what is happening with the climate this year, and in the U.S., political positioning for the 2016 election. There is increasing evidence that the overt political opposition to climate change is cracking up. There are certain aspects of the denial of climate change that are approaching such a level of exaggeration that politicians take on more absurdity than they can manage. I will also highlight some of the science-based findings that I think should bring important, new information to the motivation of taking international actions to reduce carbon dioxide emissions. I want to revisit my position that if there are any fundamental inadequacies in climate-change projections, they are aligned with the notion that we have underestimated the changes and the rate of change. I also want to bring forward and organize, more, the role of climate change in national security and international stability.

Along with the high likelihood that 2015 will flirt with being the warmest year in an awful long time, there is little doubt that the drought in California will continue to worsen. The worsening drought, which is a confluence of drought cycles, population, water demand and climate change, will offer a continuing case study in what our climate means to our well being. There are a lot of unsustainable activities in California that are coming into collision. It will not be long before more people recognize the beauty of the weather and the water in the Great Lakes states.

I am also starting a project on planning for climate change at Apostle Islands National Lakeshore. This will require me to catch up and analyze the current vigorous research on the jet stream, the Arctic oscillation and whether or not the weather is changing in response to large changes in the Arctic. The cold winter of 2014, and to a lesser extent, the cold winter of 2015, brought large numbers of visitors to Apostle Islands in the winter – think ice caves. Of course, record numbers of winter visitors were not planned for, and that stands in contrast to largely ice-free winters of most recent years. Therefore, we will be evaluating how the observations and emerging research might inform management decisions. Going back to the California drought, I am serious when I talk about people recognizing the Great Lakes states as more desirable places to live. I think managers and planners need to be looking at population trends and imagining the designs for a future of growth.

That’s enough of thinking about themes for the next few months. Look forward to the blogs being more regular than they have been in the past few weeks.

r



Ice Caves at Apostle Islands in 2014
Categories:Climate Change

Let’s call it: 30 years of above average temperatures means the climate has changed

Published: Febrero 27, 2015
Let’s call it: 30 years of above average temperatures means the climate has changed

If you’re younger than 30, you’ve never experienced a month in which the average surface temperature of the Earth was below average.

Each month, the US National Climatic Data Center calculates Earth’s average surface temperature using temperature measurements that cover the Earth’s surface. Then, another average is calculated for each month of the year for the twentieth century, 1901-2000. For each month, this gives one number representative of the entire century. Subtract this overall 1900s monthly average – which for February is 53.9F (12.1C) – from each individual month’s temperature and you’ve got the anomaly: that is, the difference from the average.

The last month that was at or below that 1900s average was February 1985. Ronald Reagan had just started his second presidential term and Foreigner had the number one single with “I want to know what love is.”

These temperature observations make it clear the new normal will be systematically rising temperatures, not the stability of the last 100 years. The traditional definition of climate is the 30-year average of weather. The fact that – once the official records are in for February 2015 – it will have been 30 years since a month was below average is an important measure that the climate has changed.



Temperature history for all Februaries from 1880-2014
NCDC



How the Earth warms

As you can see in the graphic above, ocean temperature doesn’t vary as much as land temperature. This fact is intuitive to many people because they understand that coastal regions don’t experience as extreme highs and lows as the interiors of continents. Since oceans cover the majority of the Earth’s surface, the combined land and ocean graph strongly resembles the graph just for the ocean. Looking at only the ocean plots, you have to go all the way back to February 1976 to find a month below average. (That would be under President Gerald Ford’s watch.)

You can interpret variability over land as the driver of the ups and downs seen in the global graph. There are four years from 1976 onwards when the land was below average; the last time the land temperature was cool enough for the globe to be at or below average was February 1985. The flirtation with below-average temps was tiny – primarily worth noting in the spirit of accurate record keeping. Looking at any of these graphs, it’s obvious that earlier times were cooler and more recent times are warmer. None of the fluctuations over land since 1976 provide evidence contrary to the observation that the Earth is warming.

Some of the most convincing evidence that the Earth is warming is actually found in measures of the heat stored in the oceans and the melting of ice. However, we often focus on the surface air temperature. One reason for that is that we feel the surface air temperature; therefore, we have intuition about the importance of hot and cold surface temperatures. Another reason is historical; we have often thought of climate as the average of weather. We’ve been taking temperature observations for weather for a long time; it is a robust and essential observation.



Temperature history for every year from 1880-2014.
NOAA National Climatic Data Center



Despite variability, a stable signal

Choosing one month, February in this instance, perhaps overemphasizes that time in 1985 when we had a below average month. We can get a single yearly average for all the months in an entire year, January-December. If we look at these annual averages, then the ups and downs are reduced. In this case, 1976 emerges as the last year in which the global-average temperature was below the 20th century average of 57.0F (13.9C) – that’s 38 years ago, the year that Nadia Comaneci scored her seven perfect 10s at the Montreal Olympics.

I am not a fan of tracking month-by-month or even year-by-year averages and arguing over the statistical minutia of possible records. We live at a time when the Earth is definitively warming. And we know why: predominately, the increase of greenhouse gas warming due to increasing carbon dioxide in the atmosphere. Under current conditions, we should expect the planet to be warming. What would be more important news would be if we had a year, even a month, that was below average.

The variability we observe in surface temperature comes primarily from understood patterns of weather. Many have heard of El Niño, when the eastern Pacific Ocean is warmer than average. The eastern Pacific is so large that when it is warmer than average, the entire planet is likely to be warmer than average. As we look at averages, 30 years, 10 years, or even one year, these patterns, some years warmer, some cooler, become less prominent. The trend of warming is large enough to mask the variability. The fact that there have been 30 years with no month below the 20th century average is a definitive statement that climate has changed.

The 30-year horizon

There are other reasons that this 30-year span of time is important. Thirty years is a length of time in which people plan. This includes personal choices – where to live, what job to take, how to plan for retirement. There are institutional choices – building bridges, building factories and power plants, urban flood management. There are resource management questions – assuring water supply for people, ecosystems, energy production and agriculture. There are many questions concerning how to build the fortifications and plan the migrations that sea-level rise will demand. Thirty years is long enough to be convincing that the climate is changing, and short enough that we can conceive, both individually and collectively, what the future might hold.

Finally, 30 years is long enough to educate us. We have 30 years during which we can see what challenges a changing climate brings us. Thirty years that are informing us about the next 30 years, which will be warmer still. This is a temperature record that makes it clear that the new normal will be systematically rising temperatures, not the ups and downs of the last 100 years.

Those who are under 30 years old have not experienced the climate I grew up with. In thirty more years, those born today will also be living in a climate that, by fundamental measures, will be different than the climate of their birth. Future success will rely on understanding that the climate in which we are all now living is changing and will continue to change with accumulating consequences.

This article was originally published on The Conversation.
Read the original article.

Are We Entering a New Period of Rapid Global Warming?

Published: Febrero 24, 2015
Residents of New England may understandably look back at 2015 as the year of their never-ending winter. For the planet as a whole, though, this year could stand out most for putting to rest the “hiatus”— the 15-year slowdown in atmospheric warming that gained intense scrutiny by pundits, scientists, and the public. While interesting in its own right, the hiatus garnered far more attention than it deserved as a purported sign that future global warming would be much less than expected. The slowdown was preceded by almost 20 years of dramatic global temperature rise, and with 2014 having set a new global record high, there are signs that another decade-plus period of intensified atmospheric warming may be at our doorstep.

The most compelling argument for a renewed surge in global air temperature is rooted in the Pacific Decadal Oscillation (PDO). This index tracks the fingerprint of sea surface temperature (SST) across the Pacific north of 20°N. A closely related index, the Interdecadal Pacific Oscillation (IPO), covers a larger swath of the entire Pacific. Both the PDO and IPO capture back-and-forth swings in the geography of Pacific SSTs that affect the exchange of heat between ocean and atmosphere (see Figure 1). We’ll use PDO as shorthand for both indexes in the following discussion.

The PDO typically leans toward a positive or negative state for more than a decade at a time. The positive phase, which features warmer-than-average SSTs along the U.S. West Coast, was dominant from the mid-1970s to the late 1990s. The PDO then flipped to a negative phase between about 1999 and 2013, with cooler-than-average SSTs along the West Coast. Figure 2 shows that even when a particular mode is favored, the PDO can still flip back to its opposite mode for periods of a few months or so.


Figure 1. Departures from average sea-surface temperature (degrees C) and wind (arrows) that typically prevail when the Pacific Decadal Oscillation is in its positive mode (left) and negative mode (right). Image credit: University of Washington.


It’s not clear exactly what drives the PDO, but in some ways it can be viewed as a geographically expanded version of the SST patterns created by El Niño and La Niña, averaged over a longer time period. (See Figure 2.) It’s well-established that El Niño can raise global temperature for a few months by several tenths of a degree Celsius, as warm water spreads over the eastern tropical Pacific and mixes with the overlying atmosphere. Likewise, La Niña can act to pull down global average temperature, as cooler-than-average water extends further west than usual across the tropical Pacific. The PDO mirrors these trends, but over longer periods. When the PDO is positive, there are more El Niño and fewer La Niña events, and heat stored in the ocean tends to be spread across a larger surface area, allowing it to enter the atmosphere more easily. When the PDO is negative, SSTs are below average across a larger area, and global air temperatures tend to be lower.


Figure 2. Typical warm and cool anomalies in sea-surface temperature during positive PDO years (left) and El Niño years (right). The patterns are similar, though with differences in intensity over some regions. The anomalies are reversed for negative PDO and La Niña years. Image credit: University of Washington Climate Impacts Group.


Figure 3 shows a striking connection between favored PDO modes (top) and global air temperature anomalies (bottom). The vast majority of atmospheric warming over the last century occurred during positive PDO phases, with negative PDOs tending to result in flat temperature trends. It’s easy to see how an atmospheric warming “hiatus” could occur during a negative PDO phase.


Figure 3. PDO values (top) and global air temperature anomalies (bottom). Gray shading indicates positive PDO periods, when atmospheric warming was most evident. The NOAA PDO values shown here vary slightly from those discussed in the article, which are calculated by the University of Washington. Image credit: Jerimiah Brown, Weather Underground. Data sources:NOAA (top) and NOAA/NCDC (bottom).


From the AMS meeting
The hiatus was discussed at length in a series of talks during the annual meeting of the American Meteorological Society last month in Phoenix. Jerry Meehl, from the National Center for Atmospheric Research (my former employer), gave a whirlwind 15-minute overview of hiatus-oriented research conducted over the last six years. Meehl’s talk can be viewed online. More than 20 papers have studied the hiatus and its links to the PDO/IPO, according to Matthew England (University of New South Wales). Most of the flattening of global temperature during the hiatus can be traced to cooler-than-average conditions over the eastern tropical Pacific, which pulled down global averages. An emerging theme is that natural, or internal, variability in the tropical Pacific can explain at least half of the hiatus. NCAR’s Clara Deser presented new modeling evidence along these lines (see video online). Other factors may be involved as well, including a series of weak volcanic eruptions that could explain a small part of the hiatus, according to a recent analysis by Ben Santer (Lawrence Livermore National Laboratory).

One crucial point is that global warming didn’t “stop” during the hiatus: the world’s oceans actually gained heat at an accelerated pace. Trade winds blew more strongly from east to west across the Pacific, consistent with the tendency toward La Niña conditions, as described in this open-access article by NCAR’s Kevin Trenberth and John Fasullo. Over parts of the central tropical Pacific, trade winds averaged about 3 mph stronger during 1999-2012 compared to 1976-1988. These speeds are higher than for any previous hiatus on record, bolstering the idea that other factors may have joined this negative PDO/IPO phase. The faster trade winds encouraged upwelling of cooler water to the east and helped deepen and strengthen the warm pool to the west—enough, in fact, to raise sea level around the Philippines by as much as 8 inches. Other parts of the deep ocean warmed as well. A new study led by Dean Roemmich (Scripps Institution of Oceanography) maps the areas of greatest ocean heating from 2006 to 2013 and finds that significant warming extended to depths of greater than 6600 feet.

What next for the PDO?
The PDO index, as calculated at the University of Washington, scored positive values during every month in 2014, the first such streak since 2003. By December it reached +2.51, the largest positive value for any December in records that go back to 1900. The January value from UW was 2.45, again a monthly record. (NOAA calculates its own PDO values through a closely related methodology.)

Because the PDO can flip modes for a year or more within its longer-term cycle, we don’t yet know whether a significant shift to a positive PDO phase has begun. If trade winds weaken throughout this year, and positive PDO values persist, that’ll be strong evidence that a new cycle is indeed under way. The last time we saw a two-year streak of positive values was in 1992-93. If this occurs, and assuming no spikes in major volcanic activity, we could expect greater rises in global temperature over the next 10 to 15 years than we’ve seen during the hiatus. In addition, we should watch for El Niño to make its presence known more often.

“I am inclined to think the hiatus is over, mainly based on the PDO index change,” NCAR’s Kevin Trenberth told me. While Matthew England isn’t ready to offer such a prediction, he emphasized that any post-hiatus global temperature rise is likely to be fairly rapid. Trenberth also commented on an interesting NOAA analysis (see Figure 4): “If one takes the global mean temperature from 1970 on, everything fits a linear trend quite well except 1998.”


Figure 4. When looking at global temperature over a full PDO cycle (1970s to 2010s), the overall rise becomes evident, despite the flattening observed in the last 15 years. Image credit: NOAA.


A record-strong El Niño occurred in 1998, providing an unusually powerful boost to global temperature and fueling years of subsequent declarations that “global warming stopped in 1998.” The record warmth of 2014 made it clear that global warming has no intention of stopping, and the next few years are likely to reinforce that point. Nevertheless, snowbound New Englanders, and millions of other easterners now dealing with record cold for so late in the year, may be wondering why eastern North America has seen so much cold and snow in the past few winters--especially this one--and how long that climatic quirk might continue. Stay tuned for a separate post on that topic.

Bob Henson
Categories:Climate Change

New England Intense Hurricanes Much More Numerous 340 to 1800 Years Ago

Published: Febrero 17, 2015
Numerous Category 3 and 4 hurricanes frequently pounded New England during the first millennium, from the peak of the Roman Empire into the height of the Middle Ages, said a study accepted for publication this month in the open-access journal Earth’s Future, Climate Forcing of Unprecedented Intense-Hurricane Activity in the Last 2,000 Years. These prehistoric hurricanes were stronger than any hurricane documented to hit the region since the mid-1800s, and would be catastrophic if they hit the region today, according to Jeff Donnelly, a scientist at Woods Hole Oceanographic Institution (WHOI) in Massachusetts and lead author of the new paper. In a press release, Donnelly said, “We hope this study broadens our sense of what is possible and what we should expect in a warmer climate. We may need to begin planning for a category 3 hurricane landfall every decade or so rather than every 100 or 200 years.”


Figure 1. The storm surge from Category 2 Hurricane Carol in 1954 batters New England's Edgewood Yacht Club near Providence, Rhode Island. Image credit: NOAA Photo Library.

The paper is the latest contribution to the field of paleotempestology--the study of past tropical cyclone activity by means sediment deposits, cave speleothems, tree rings, coral deposits, as well as historical documentary records. In this case, the researchers took sediment cores from Salt Pond near Falmouth on Cape Cod, Massachusetts. The pond is separated from the ocean by a 1.3- to 1.8-meter (4.3- to 5.9-foot) high sand barrier. Over hundreds of years, storm surges from Category 2 and stronger hurricanes have deposited sediment over the barrier and into the pond. The scientists were able to calibrate the timing of the intense hurricane strikes by dating the layers from Category 2 Hurricane Bob of 1991, the 1675 (September 7) New England hurricane, and the Great Colonial Hurricane of 1635, which passed across southeastern New England and caused widespread damage consistent with a category 3 hurricane.


Figure 2. Scientists collect a sediment core from Salt Pond in Falmouth, Massachusetts, to study hurricane overwash deposits placed there by storm surges from intense hurricanes. The aluminum tube was vibrated into the muddy sediment at the bottom of the pond and then extracted with a hoist. Image Credit: WHOI

The prehistoric sediments showed that there were two periods of elevated intense hurricane activity on Cape Cod--from 150 to 1150, and from 1400 to 1675. Previous paleotempestology studies also found evidence of high hurricane activity during 150 - 1150 A.D. from the Caribbean to the Gulf Coast. Both time periods had unusually warm sea surface temperatures (SSTs) in the Main Development Region for hurricanes, from the Caribbean to the coast of Africa. Warm ocean temperatures in this region have been linked to increased intense hurricane activity by a number of recent research papers. In recent decades, ocean temperatures in the Main Development Region have surpassed the warmth of prehistoric levels, and these waters are expected to warm further over the next century as the climate heats up, suggesting that intense hurricane activity in New England may return to the levels of 340 to 1800 years ago. However, other factors besides warming SSTs will also shape what happens in the North Atlantic. For example, the pattern of ocean warming could bring more El Niño-style wind shear to the Atlantic, reducing hurricane activity. Still, New England would be wise to take heed of Donnelly's advice that we may need to begin planning for a category 3 hurricane landfall every decade or so rather than every 100 or 200 years.

Jeff Masters
About the Blogs
These blogs are a compilation of Dr. Jeff Masters,
Dr. Ricky Rood, and Angela Fritz on the topic of climate change, including science, events, politics and policy, and opinion.
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