This is a busy time of year for the sciences with the annual American Geophysical Union’s and the international Conference of Parties meetings occurring simultaneously. NOAA has issued a number of reports in recent days, none of which are overflowing with good news. Today, NOAA released their Global Sea Level Rise Scenarios for the United States National Climate Assessment. It was produced in response to a request from the U.S. National Climate Assessment Development and Advisory Committee and consists of a review and synthesis of recent scientific publications examining global sea level change.
Why is this report important? “More than 8 million people in the US live in areas at risk of coastal flooding. Along the Atlantic Coast alone, almost 60 percent of the land that is within a metre of sea level is planned for further development, with inadequate information on the potential rates and amount of sea level rise.” The public, policymakers and planners need to know what to expect with respect to sea-level rise this century: where should development occur or be restricted and why?
The report is based on four plausible scenarios. Scenario 1 is simply a linear extrapolation of the historical sea-level rise (SLR) rate out to 2100. Scenario 2 is based only on projected ocean warming. Scenario 3 builds on 2 by adding recent ice sheet loss (land-based). Scenario 4 reflects ocean warming and the maximum plausible contribution of ice sheet loss and glacial melting. Scenario 1 is appropriate for communities which can assume high risk or for short-term projects. Scenario 4, in contrast, is meant for places which can’t accept risk.
Here are the scenario SLR values by 2100:
Note that these values are not predictions, but are projections. That is, NOAA isn’t saying that if X and Y happen, then the Intermediate-High scenario is a prediction. The scenarios present a framework for policymakers and the public to use to make decisions.
Here is a time series graph of historical and projected SLR:
The range of potential SLR shown in the table and figure above might lead some to conclude that ‘high confidence” in that range is misplaced by NOAA. This is a gross misinterpretation of what is presented. The level of uncertainty, which will always exist, is actually useful to policymakers. Given this range of projections, people can leverage local and regional knowledge to come to better decisions than they would without this range. Something quantified is better than a big shrug when planning, after all.
With the governors of New York, New Jersey, and Connecticut requesting $80 Billion to clean up and rebuild (better) after Hurricane Sandy, future projections of sea-level rise can obviously provide guidance regarding what and how to rebuild in addition to where to rebuild. Policy development and planning will have to take these and other projections into heavier account this century than they did last century. An estimate of how many billions of dollars can potentially be saved by incorporating this information would also be useful.
According to data released by NASA and NOAA this week, October 2012 was the 2nd and 4th warmest October’s (respectively) globally on record. NASA’s analysis produced the 2nd warmest October in its dataset; NOAA recorded the 4th warmest October in its dataset. The two agencies have slightly different analysis techniques, which in this case resulted in not only different temperature anomaly values but somewhat different rankings as well.
The details:
October’s global average temperatures were 0.69°C (1.24°F) above normal (1951-1980), according to NASA, as the following graphic shows. The warmest regions on Earth coincide with the locations where climate models have been projecting the most warmth to occur for years: high latitudes (especially within the Arctic Circle in July 2012). The past three months have a +0.63°C temperature anomaly. And the latest 12-month period (Nov 2011 – Oct 2012) had a +0.51°C temperature anomaly. The time series graph in the lower-right quadrant shows NASA’s 12-month running mean temperature index. The recent downturn (post-2010) is largely due to the latest La Niña event (see below for more) that recently ended. ENSO conditions returned to a neutral state. Therefore, the temperature trace (12-mo running mean) should track upward again, especially as cooler months fall off the running mean.
Figure 1. Global mean surface temperature anomaly maps and 12-month running mean time series through October 2012 from NASA.
According to NOAA, October’s global average temperatures were 0.63°C (1.13°F) above the 20th century mean of 14.0°C (57.2°F). NOAA’s global temperature anomaly map for October (duplicated below) reinforces the message: high latitudes continue to warm at a faster rate than the mid- or low-latitudes.
The two different analyses’ importance is also shown by the preceding two figures. Despite differences in specific global temperature anomalies, both analyses picked up on the same temperature patterns and their relative strength.
The continued anomalous warmth over Siberia is especially worrisome due to the vast methane reserves locked into the tundra and under the seabed near the region. Methane is a stronger greenhouse gas than carbon dioxide over short time-frames (<100y),which is the leading cause of the warmth we’re now witnessing. As I discussed in the comments in post this summer, the warming signal from methane likely hasn’t been captured yet since the yearly natural variability and the CO2-caused warming signals are much stronger. It is likely that we will not detect the methane signal for many more years.
Of additional concern are the very warm conditions found over Greenland. Indeed, record warmth was observed at a 3200m altitude station in early July. 3.6°C may not sound that warm in July, but the station’s location at 10,500ft altitude is of interest. In contrast, continued warmth over portions of Greenland that have not witnessed such warmth did result in rapid melting during 2012. There was recent news that described how much faster melt has occurred over Greenland (see associated picture) than expected in the IPCC AR4. While the record-setting sea ice melt across the Arctic Ocean this year is important in some respects, at least melting sea ice doesn’t contribute to sea level rise. The opposite is true for Greenland melt: every drop that makes it to the ocean raises the level. When the melt is happening 3X faster than just 20 years ago, it’s time to pay attention (note: not panic!).
These observations are also worrisome for the following reason: the globe is experiencing ENSO-neutral conditions:
As the second time series graph (labeled NINO3.4) shows, the last La Niña event hit its highest (most negative) magnitude more than once between November 2011 and February 2012. Since then, SSTs peaked at +0.8 in September (y-axis). You can see the effect on global temperatures that the last La Niña had via this NASA time series. Both the sea surface temperature and land surface temperature time series decreased from 2009 to 2011. Note that the darker lines (running means) started to increase at the end of 2011, following the higher frequency monthly data. ENSO-nuetral conditions are expected to continue through the next 3-6 months, after which a new El Niño event might begin.
As the globe returns to ENSO-neutral conditions this winter, how will global temperatures respond? Remember that global temperatures typically trail ENSO conditions by 3-6 months: the recent tropical Pacific warming trend should therefore help boost global temperatures back to their most natural state (i.e., without an ENSO (La Niña) signal on top of it, although other important signals might also occur at any particular point in time).
So what do we do? I hope most readers are aware that the 18th Conference of Parties (COP-18) meeting is currently underway in Doha, Qatar. I’ve stated my opinion before that I don’t think putting every country in the world around the table to negotiate a climate treaty is the most appropriate approach. Canada, Russia, and Japan removed themselves from the Kyoto Protocol recently, which means that the only large emitters left are from the European Union. I actually think that’s more appropriate: I prefer regional and bilateral agreements – countries should have pursued them more aggressively in the past 30 years.
More to the point, we should focus on bottom-up approaches. There are smaller groups of people who, if provided the right type of expertise and resources when needed, could probably enact changes that will result in decreasing emissions as well as successful adaptation policies. The developed world is decarbonizing, but not fast enough yet. I also recommend you watch China. They invested very large sums of money in renewable energy and other green efforts. That money will bear fruit in the future. The rub, of course, is we cannot accurately predict when and how today. It will also be interesting to see how the northeast U.S. reacts to Hurricane Sandy. They have to rebuild infrastructure. Will they include adaptive measures while they’re at it or will they kick the can down the road?
Judging by recent search terms used to get to this blog and the relative recent peak in traffic, readers have been searching for this post. I wanted to wait a little longer into the month so that I could capture the expected Arctic minimum, which officially occurred on the 16th of September. The NSIDC announced this date, after which I started gathering the plots that are found below. This post will be longer than it usually is because this year’s minimum shattered the record minimum set in 2007, which shattered the previous record set in 2005. Most of the post is made up of figures, so I encourage readers to at least view them to get a good picture of today’s conditions. I’m purposefully framing things this way to relay the truly stunning situation the Arctic is in today. 2012 is additional proof the Arctic cryosphere is searching for a new stable point, but hasn’t found it yet. That does not bode well for the rest of the globe. With that, let’s begin.
The state of global polar sea ice area in mid-September 2012 remains significantly below climatological normal conditions (1979-2009). Arctic sea ice loss is solely responsible for this condition. In fact, if Antarctic sea ice were closer to its normal value, the global area would be much lower than it is today. Arctic sea ice melted quickly in August and the first half of September because it was thinner than usual and winds helped push ice out of the Arctic where it could melt at lower latitudes; Antarctic sea ice has refrozen at a faster than normal rate during the austral winter. Polar sea ice recovered from an extensive deficit of -2 million sq. km. area late last year to a +750,000 sq. km. anomaly in March 2012 before falling back to a -2.2 million sq. km. deficit earlier this month.
After starting the year at a deficit from normal conditions, sea ice area spent an unprecedented length of time near the -2 million sq. km. deficit in the modern era in 2011 (i.e., almost the entire calendary year). Generally poor environmental conditions (warm surface temperatures and certain wind patterns) established and maintained this condition, predominantly across the Arctic last year. The last time global sea ice area remained near 19 million sq. km. during May was in 2007, when the Arctic extent hit its modern day record minimum. The maximum in the boreal spring the past two years was ~19.5 million sq. km.
Conditions were prime for another modern-day record sea ice extent minimum to occur in September. Specific weather conditions helped to determine how 2012′s extent minimum ranks compared to the last 33 years, but it was the overall poor condition of Arctic sea ice that contributed to this year’s record low values.
According to data released by NASA and NOAA this week, July 2012 was the 12th and 4th warmest July (respectively) globally on record. NASA’s analysis produced the 12th warmest July in its dataset; NOAA recorded the 4th warmest July in its dataset. The two agencies have slightly different analysis techniques, which in this case resulted in not only different temperature anomaly values but rather different rankings as well.
The details:
July’s global average temperatures were 0.47°C (0.85°F) above normal (1951-1980), according to NASA, as the following graphic shows. The warmest regions on Earth coincide with the locations where climate models have been projecting the most warmth to occur for years: high latitudes (especially within the Arctic Circle in July 2012). The past three months have a +0.56°C temperature anomaly. And the latest 12-month period (Aug 2011 – Jul 2012) had a +0.50°C temperature anomaly. The time series graph in the lower-right quadrant shows NASA’s 12-month running mean temperature index. The recent downturn (post-2010) is largely due to the latest La Niña event (see below for more) that recently ended. As ENSO conditions return to neutral or even El Niño-like, the temperature trace should track upward again.
Figure 1. Global mean surface temperature anomaly maps and 12-month running mean time series through July 2012 from NASA.
According to NOAA, July’s global average temperatures were 0.63°C (1.13°F) above the 20th century mean of 15.2°C (1.12°F). NOAA’s global temperature anomaly map for July (duplicated below) reinforces the message: high latitudes continue to warm at a faster rate than the mid- or low-latitudes. Unfortunately in July 2012, almost the entire Northern Hemisphere was warmer than normal.
These figures show just how extreme (intensity & spatial extent) the heat wave over most of the US was during July 2012. As many people saw during the preceding two-and-a-half weeks, England was cooler than usual. The same was true for northwestern Europe, most of Australia, and a good portion of South America (Argentina, Bolivia, etc.) Additional anomalous warmth occurred over Greenland, Russia, eastern Europe, and into central Asia and the Middle East. The two different analyses’ importance is also shown by these figures. Despite differences in specific global temperature anomalies, both analyses picked up on the same temperature patterns and their relative strength.
The continued anomalous warmth over Siberia is especially worrisome due to the vast methane reserves locked into the tundra and under the seabed near the region. Methane is a stronger greenhouse gas than carbon dioxide over short time-frames (<100y),which is the leading cause of the warmth we’re now witnessing. As I discussed in the comments in a recent post, the warming signal from methane likely hasn’t been captured yet since the yearly natural variability and the CO2-caused warming signals are much stronger. It is likely that we will not detect the methane signal for many more years. Of additional concern are the very warm conditions found over Greenland. Indeed, record warmth was observed at a 3200m altitude station in early July. 3.6°C may not sound that warm in July, but the station’s location at 10,500ft altitude is of interest. I want to post more on this later, but the early July melt occurred over a very short time period, which did not result in a great deal of runoff. In contrast, continued warmth over portions of Greenland that have not witnessed such warmth did result in rapid melting during 2012 (note: the melt season isn’t over yet either).
These observations are also worrisome for the following reason: the globe is still returning to ENSO-neutral conditions:
As the second time series graph (labeled NINO3.4) shows, the last La Niña event hit its highest (most negative) magnitude more than once between November 2011 and February 2012. Since then, SSTs have slowly warmed back above a +0.5°C-1.0°C anomaly (y-axis). La Niña is a cooling event of the tropical Pacific Ocean that has time-delayed effects across the globe. It is therefore significant that the past handful of months’ global temperatures continued to rank in or near the top-5 warmest in the modern era. You can see the effect on global temperatures that the last La Niña had via this NASA time series. Both the sea surface temperature and land surface temperature time series decreased from 2009 to 2011. Note that the darker lines (running means) started to increase at the end of 2011, following the higher frequency monthly data.
As the globe returns to ENSO-neutral conditions this summer and early fall, how will global temperatures respond? Remember that global temperatures typically trail ENSO conditions by 3-6 months: the recent tropical Pacific warming trend should therefore help boost global temperatures back to their most natural state (i.e., without an ENSO signal on top of it, although other important signals might also occur at any particular point in time). Looking further into the future, what will next year’s temperatures be as the next El Niño develops, as predicted by a number of methods (see figure below)?
Figure 5. Set of mid-July predictions of ENSO conditions by various models (dynamical and statistical). To be considered an El Niño event, 3-month average temperature anomalies must be measured above +0.5°C for 5 consecutive months (so the earliest an El Niño event is likely to be announced is sometime this fall). Approximately 1/2 of the models are predicting a new El Niño event by the end of this year. The other models predict ENSO-neutral conditions through next spring.
From the above, I hope it is clear that the US’s recent record heat wave and historic drought are associated with the most recent La Niña event. This is typical for the US, given dominant wind patterns that La Niña establishes. While El Niño would add additional anomalous warmth on top of the slowly evolving climate change signal, it usually also heralds above-average precipitation over most of the US. That would be a welcome event, given the reach and severity of the drought currently underway.
The state of global polar sea ice area in early August 2012 remains significantly below climatological normal conditions (1979-2009). Arctic sea ice loss is solely responsible for this condition during this boreal summer. Arctic sea ice melted quickly in July because it was thinner than usual and winds helped push ice out of the Arctic where it could melt at lower latitudes; Antarctic sea ice has refrozen at a slightly above normal rate during the austral winter. Polar sea ice recovered from an extensive deficit of -2 million sq. km. area late last year to a +750,000 sq. km. anomaly in March 2012 before falling back to a -1.8 million sq. km. deficit.
After starting the year at a deficit from normal conditions last year, sea ice area spent an unprecedented length of time near the -2 million sq. km. deficit in the modern era in 2011. Generally poor environmental conditions (warm surface temperatures and certain wind patterns) established and maintained this condition, predominantly across the Arctic last year. Conditions were slightly “better” than they were in 2007 or even in 2011 during July. As we know from past experience, that can change rather quickly as Arctic sea ice melts in August and early September on its way to its yearly minimum.
Conditions are prime for another modern-day record sea ice extent minimum to occur in early September. Specific weather conditions over the next month will determine how 2012′s extent minimum ranks compared to the last 33 years. There is a very impressive low pressure system currently in the Arctic Ocean; a strong storm that normally doesn’t occur in July/August. This might seem at first to indicate that sea ice melt might not occur, but the energy being exerted on the ocean and ice is actually more likely to assist in ice melt. This is because of the turbulent motion imparted on the ocean by the storm’s winds, which repeatedly submerge ice in warmer water. The winds also bring warmer sub-surface water up to the surface. After the storm clears and within the following week, we shall see what effects the storm had on the thin Arctic ice. The concentration maps below in particular will take a few days to report the effect – they are five-day averages of measurements so that spurious data do not unduly affect ice condition assessment.
Arctic Ice
According to the NSIDC, the weather conditions that caused less freezing to occur on the Atlantic side of the Arctic Ocean and more freezing on the Pacific side shifted in late spring/early summer this year to conditions that aided rapid melting across the Arctic – a continuation of similar events in the past six years. Sea ice melt during July was not the fastest on record: 2.97 million sq. km. vs. 3.53 million sq. km. in July 2007! Still, July′s extent was far below average for the month, as some of the graphs below demonstrate. In fact, the extent set multiple daily record lows in July, as shown by one of the graphs below. Arctic sea ice extent on in July averaged 7.94 million sq. km. Ice in the Laptev, East Siberian and Kara Seas remained very much below normal, themselves setting daily record lows during July. The Bering Sea, which saw ice extent growth due to anomalous northerly winds in the late winter/early spring witnessed the record high extent melt back to zero in an extremely short time period earlier this year. The NSIDC included the following in their analysis:
Temperatures at the 925 hPa level (about 3,000 feet above the ocean surface) were typically 1 to 3 degrees Celsius (1.8 to 5.4 degrees Fahrenheit) above the 1981 to 2010 average over the Beaufort Sea and regions to the north, as well as over Baffin Bay. By contrast, temperatures were 1 to 3 degrees Celsius below average over the Norwegian Sea.
In terms of longer, climatological trends, Arctic sea ice extent in July has decreased linearly by 7.1% per decade. This rate is lowest in the spring months and highest in late summer/early fall months. Note that this rate also uses 1979-2000 as the climatological normal. There is no reason to expect this rate to change significantly (more or less negative) any time soon. Additional low ice seasons will continue. Some years will see less decline than other years (like this past year) – but the multi-decadal trend is clear: significantly negative. The specific value for any given month during any given year is, of course, influenced by local and temporary weather conditions. But it has become clearer every year that humans helped establish a new normal in the Arctic with respect to sea ice. This new normal will continue to have far-reaching implications on the weather in the mid-latitudes, where most people live.
Arctic Pictures and Graphs
The following graphic is a satellite representation of Arctic ice as of July 7, 2012:
Figure 1 – UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20120707.
Compare this with August 6th’s satellite representation, also centered on the North Pole:
The sea ice in the Canadian archipelago and along the northern coast of Russia determine whether the Northwest and Northeast passages open up or not. You can see by comparing the two graphs that the ice is nearly completely melted in the Canadian archipelago. The ice is also mostly melted along the entire northern coast of Russia – just a little remains in the Eastern Siberian sea. Last year, both passages opened again. I continue to think that the Northern Passage will likely open sometime this month. The Northeastern Passage might not open this year, but if it doesn’t, it won’t do so by a thin margin. You can also see in Figure 2 that the dominant wind direction has been toward Greenland. This allows ice to stack up against a landmass and not be exported as quickly out into the Atlantic Ocean where it is likelier to melt. The aforementioned Arctic Ocean storm has shifted wind direction somewhat across the basin, so I don’t expect all of the ice in Figure 2 to remain come September.
Overall, the health of the remaining ice pack is not healthy, as the following graph of Arctic ice volume from the end of July demonstrates:
Figure 3 – PIOMAS Arctic sea ice volume time series through July 2012.
As the graph shows, volume hit another record minimum in June 2012. Moreover, the volume is far, far outside the 2 standard deviation envelope (lighter gray contour surrounding the darker gray contour and blue median value). Figure 3 demonstrates how anomalous conditions are for sea ice in the Arctic. The volume has exceed the -4 standard deviation this year as well as the past two years. I understand that most readers don’t have an excellent handle on statistics, but conditions between -1 and -2 standard deviations are not very common; conditions outside the -2 standard deviation threshold (see the line below the shaded area on the graph above) are incredibly rare: the chances of 3 of them occurring in 3 subsequent years under normal conditions are extraordinarily low. Hence my assessment that “normal” conditions in the Arctic are shifting from what they were in the past few centuries: a new normal is developing. Note further that after conditions returned to near the -1 standard deviation envelope in late 2011/early 2012, as it did in early 2011, volume has once again fallen rapidly outside of the -2 standard deviation area. That means that natural conditions are not the likely cause; rather, another cause is much more likely to be responsible for this behavior.
I found a new graph that shows this and some additional information in a slightly different way:
Figure 4 – PIOMAS Arctic Sea Ice Volume from 1980 through July 2012.
This figure shows volume as a function of date. 2012 is the red curve, which is plotted against the average volume of 2010 through July 2012 (yellow), the average volume of the 2000s (green), the average volume of the 1990s (blue), and the average value of the 1980s (violet). Individuals years from 1979-2011 are indicated by the light gray curves. It is once again clear how anomalous recent conditions are compared to conditions from the latter part of the 20th century. It further shows how rapidly conditions have changed: the volume differences implied by this graph are astounding. The minimum volume typically occurs in early September, which we are approaching again in 2012.
Switching back from volume to area, take a look at July’s areal extent time series data:
This is the time series graph that the NSIDC occasionally includes in their monthly reports. I present only this graph and not the graph updated daily throughout the month because of the historical context this graph provides. The ice that piled up in the winter wasn’t thick enough to prevent rapid melt to occur (see early June 2012). The effect of the thickening over the winter on September’s minimum extent will indicate how helpful the early season winds were in building sea ice that doesn’t melt every year back up. Right now, the situation doesn’t look good for September extent. During June, as I wrote above, melting occurred at record rate, resulting in a return to record low extent conditions by the middle of June. 2012′s extent has been below 2007′s for over two months and has been challenging all-time daily record minimums for almost two months. You can also see in this time series graph that conditions since 2007 have clearly differed from the normal conditions established from 1979-2000 (light gray contours surrounding the dark gray mean value).
Figure 6 – NSIDC northern hemisphere sea ice area (not extent) from the past two years only (blue) and the 1979-2008 mean (gray). The red curve shows the anomaly from the mean.
Note in Figure 6 how low the sea ice area is in the beginning of August 2012: -2.157 million sq. km.! Note two additional things. 1) The 2012 area value already is less than the climatological mean value by ~1.5 million sq. km. 2) The 2012 area value is only ~0.5 million sq. km. higher than the minimum recorded in 2011. The area value has slid just slightly under 3 million sq. km. only twice before: 2007 and 2011. Unless weather conditions change radically in the next couple of weeks, 2012 is also very likely to witness another sea ice area value under 3 million sq. km. The link above also shows that sea ice area was lower than 4 million sq. km. only during the past 5 years. Back in the 1980s, the area didn’t fall beneath 5 million sq. km. except for two years (1984, 1989). This is simply another way of noting that the Arctic environment has changed substantially in the past generation. One more note about the anomaly value (-2.157 here): 2007′s lowest anomaly currently ranks as the modern-day record: -3.6 million sq. km. 2012′s anomaly value is obviously far away from that, but has spent the most time below -2 million sq. km. than any year except 2007.
Antarctic Pictures and Graphs
Here is a satellite representation of Antarctic sea ice conditions from July 7th:
Ice gain is less easily visible around the continent than it was a few months ago. As a reminder, the difference between long-term Arctic ice loss and lack of Antarctic ice loss is largely and somewhat confusingly due to the ozone depletion that took place over the southern continent in the 20th century. This depletion has caused a colder southern polar stratosphere than it otherwise would be, reinforcing the polar vortex over the Antarctic Circle. That vortex has helped keep cold, stormy weather in place over Antarctica that might not otherwise would have occurred to the same extent and intensity. As the “ozone hole” continues to recover during this century, the effects of global warming will become more clear in this region, especially if ocean warming continues to melt sea-based Antarctic ice from below. For now, we should perhaps consider the lack of global warming signal due to lack of ozone as relatively fortunate.
Finally, here is the Antarctic sea ice extent time series from August 6th:
Antarctic sea ice extent had remained at or above average to some extent through the late austral fall and through the austral winter, which is good news. The difference in conditions from the first part of 2011 to the similar time period in 2012 is obvious: NSIDC measured last July’s extent near the bottom of the standard deviation envelope while this year’s extent is much healthier.
Errata
Here are my State of the Poles posts from July and June.
I’ve written a couple of posts on climate change basics (Gases, Forcing & Surface Temperature and Energy & Projections) that described how energy enters and moves through the climate system and some physical ramifications of emitting greenhouse gases. This post will build on those in an important way by examining what is very likely to happen to the base climate system in response to increasing carbon emissions. The operative word that is used throughout is: permanency. The climate system has so far been slightly altered by our species’ emissions. Most of the effects of that alteration won’t go away for hundreds of years. As humans emit additional emissions, the effects grow.
For all intents and purposes, as far as our species is concerned, the climate system’s alteration will not go away for a long, long time – on the order of thousands of years. That’s permanency as far as we’re concerned. Or, as the paper I cite puts it: it’s irreversible. Conditions will very likely not return to those we’ve experienced in our lifetimes and in the past few thousand years for many thousands of years into the future. That’s the cold, hard scientific truth of the situation. Now, people can decide for themselves whether such irreversibility or permanency is a “good” or “bad” thing – I won’t make normative judgments for anyone else but myself. I don’t consider such a change a “good” thing. The effects I will describe here are significant, but they are only those that are easily projected. Many other effects that haven’t been considered or experienced by our species will almost certainly fall out as a result of projections discussed here. Our civil institutions are not well equipped to handle even the first-order effects, let alone the compounding influence of effects upon effects.
On a personal note, I will not describe things as ‘catastrophic’ anymore. I have hinted at this in some posts I’ve written in the past few months without much explanation. The primary reason for this is using such language simply turns people off from considering the material. I think we need more people engaged on this topic, not less, and will consider scientific results of language and framing as much as I consider climate science results (a post dealing with this specifically is in the works). That said, I will continue to not spend many resources to engage the ideologically driven skeptic community. They simply have a different worldview than I do and neither party will convince the other that their side is “correct”. One goal of this blog is to inform those who are interested and to have civil, productive discussions of peer-reviewed climate science and the political/policy implications of that science.
So, before I delve into some details, words like `permanency` and `irreversible` will be used more frequently on this blog in the future. I will not use words like catastrophic. On that note…
Susan Solomon and her coauthors published a paper in 2008 entitled, “Irreversible climate change due to carbon dioxide emissions.” The primary finding: climate change resulting from anthropogenic carbon dioxide emissions is largely irreversible for 1,000s of years after the emissions stop. As a result, atmospheric temperatures are likely to remain higher than present-day values, rainfall reductions during dry seasons are likely to occur across the planet, and sea level rise is likely to continue to occur for thousands of years even though the models they used did not include every physical process involved in the hydrologic cycle in addition to the noted lack of all first-order forcings. The study gives us an idea of the type of temperature trends we are likely to experience for the next few thousand years as well as a conservative estimate of how high average global sea level rise will be.
In similar fashion as other modeling work, Solomon et al. allow CO2 concentrations to rise, then halt suddenly at some level in the future (reflecting a dramatic shift in human behavior such as radical technological innovation, etc. I characterize this treatment of behavior as “magical” because there is never robust reasoning to adequately describe such behavior shifts). Concentrations in the study rose at 2%/year to peak CO2 values of 450, 550, 650, 750, 850, and 1200 ppmv, followed by zero emissions after hitting each peak. For reference, current annual CO2 concentrations average just over 390pppmv. What occurs after the peaks is the interesting part of this paper, as the following graph shows:
The x-axis shows time in years out to the year 3000. Pre-industrial CO2 concentrations are indicated by the dashed line near the bottom of the graph. Without any effort at emissions’ mitigation, any one of these peaks is well within the realm of possibility. What happens after each peak? An extended period of time during which CO2 concentrations remain much higher than pre-industrial levels. Concentrations remain at levels between ~300 to ~800ppmv for the next thousand years, decreasing at decreasing rates during and after they reach their respective peaks. What effect might this have on temperature? The next graph in the paper demonstrates the simulated effects:
Each curve in this graph corresponds to the emissions lines in the previous graphs. Temperatures remain at least 1°C warmer (and up to 4°C warmer) than those of the year 1800 for the next thousand years. Temperatures do not decline at nearly the rate that CO2 concentrations do in the latter part of the millenium. While CO2 concentrations remain higher throughout the period, “permanency” is evident by temperature trends through the year 3000. What does that mean for the real world? Whatever temperature shift takes place through the end of rising emissions stays in place for all intents and purposes for our species permanently.
Rising temperatures have many other effects on different earth systems, including sea levels. Here are the sea level change projections from the Solomon et al. study:
Again, each line in this plot corresponds to an emissions scenario and a temperature trace in the two previous plots. Note the y-axis on this plot: it only shows sea level rise due to thermal expansion. Any additional water entering the world’s oceans resulting from melting glaciers or land-based ice sheets are not included in this projection. Therefore, the reader can interpret this plot as a minimum of sea level rise through 3000. The greatest rise obviously corresponds to the highest emissions scenario and the highest temperature rise. 0.4m rise in the minimum projected by this study and 1.9m is the maximum. Similarly to the previous plots, sea level doesn’t decrease once emissions and temperatures stabilize. Instead, they continue to slowly increase throughout the next millenium and remain high in essence in a permanent sense.
What’s obviously inaccurate with this study is the instantaneous cessation of CO2 emissions. Many studies treat future emissions in similar fashion. How emissions decrease in the future is of course a large unknown and therefore impossible to model with high accuracy. Solomon et al. do acknowledge that their treatment of emissions is not meant to be realistic, but to “represent a test case whose purpose is to probe physical climate system changes”. The primary lesson from this paper is relevant no matter the specific future emissions pathway: the longer emissions continue at any level close to 20th century levels, the longer it will take before concentrations stop rising and begin their slow descent in a planet with full carbon sinks, and temperatures and sea levels stabilize. The point at which all of these conditions peak is, in the end, almost entirely up to us.
The policy implications of this and other studies are obvious and not-so-obvious. Among the former: the willingness of coastal residents to incur higher infrastructure and other costs in future years versus their desire to implement policies designed to mitigate their situation; the willingness of non-coastal residents to keep funding federal insurance programs that allow others to live in high-risk zones; the way in which municipalities write zoning laws: for developers or for citizens; policy development that will help populations adapt to climate change effects in their region and/or that address mitigation on a larger scale; the priority assigned to programs that may or may not generate technological innovations that would lead to adaptive or mitigative strategies at some undefined point in the future (via government or business); how to address the need that policymakers have for information that will facilitate a balanced approach between short-term gain and long-term risk management. Other implications exist, as I’m sure most readers can attest. One result of this study is clear: we have locked in a certain amount of costs just as we’ve locked in a certain amount of warming and subsequent changes in multiple earth systems.
According to data released by NASA and NOAA this week, June 2012 was the 4th warmest June globally on record. NASA’s analysis produced the 4th warmest June in its dataset; NOAA recorded the 4th warmest May in its dataset. The two agencies have slightly different analysis techniques, which actually helps to reinforce the results from each other.
The details:
June’s global average temperatures were 0.56°C (1.01°F) above normal (1951-1980), according to NASA, as the following graphic shows. The warmest regions on Earth coincide with the locations where climate models have been projecting the most warmth to occur for years: high latitudes (especially within the Arctic Circle in June 2012). The past three months have a +0.59°C temperature anomaly. And the latest 12-month period (Jul 2011 – Jun 2012) had a +0.52°C temperature anomaly. The time series graph in the lower-right quadrant shows NASA’s 12-month running mean temperature index. The recent downturn (post-2010) is largely due to the latest La Niña event (see below for more) that recently ended. As ENSO conditions return to normal, the temperature trace should track upward again.
Figure 1. Global mean surface temperature anomaly maps and 12-month running mean time series through June 2012 from NASA.
According to NOAA, June’s global average temperatures were 0.63°C (1.13°F) above the 20th century mean of 15.5°C (59.9°F). NOAA’s global temperature anomaly map for June (duplicated below) reinforces the message: high latitudes continue to warm at a faster rate than the mid- or low-latitudes. Unfortunately in June 2012, almost the entire Northern Hemisphere was warmer than normal.
Figure 2. Global temperature anomaly map for June 2012 from NOAA.
The extreme warmth over Siberia is especially worrisome due to the vast methane reserves locked into the tundra and under the seabed near the region. Methane is a stronger greenhouse gas than carbon dioxide over short time-frames (<100y),which is the leading cause of the warmth we’re now witnessing. As I discussed in the comments in a recent post, the warming signal from methane likely hasn’t been captured yet since the yearly natural variability and the CO2-caused warming signals are much stronger. It is likely that we will not detect the methane signal for many more years. Of additional concern are the very warm conditions found over Greenland. Indeed, record warmth was observed at a 3200m altitude station earlier this month. 3.6°C may not sound that warm in July, but look at the station’s location:
Figure 3. Location of Summit Camp, Greenland.
The station is in the middle of the massive Greenland ice sheet at ~10,500ft elevation. It is difficult to warm this area enough to register above freezing temperatures. Multiple stations on the top of the ice sheet similarly observed record warm temperatures recently. What happens when air temperatures are above freezing with the mid-summer sun shining down for most of the day? Record flooding occurs.
These observations are also worrisome for the following reason: the globe is still exiting the latest La Niña event:
As the second time series graph (labeled NINO3.4) shows, the last La Niña event hit its highest (most negative) magnitude more than once between November 2011 and February 2012. Since then, SSTs have slowly warmed back toward a +0.5°C anomaly (y-axis). La Niña is a cooling event of the tropical Pacific Ocean that has effects across the globe. It is therefore significant that the past handful of months’ global temperatures continued to rank in or near the top-5 warmest in the modern era. You can see the effect on global temperatures that this last La Niña had via this NASA time series.
As the globe returns to ENSO-neutral conditions this summer and early fall, how will global temperatures respond? Remember that global temperatures typically trail ENSO conditions by 3-6 months: the recent tropical Pacific warming trend should therefore help boost global temperatures back to their most natural state (i.e., without an ENSO signal on top of it, although other important signals might also occur at any particular point in time). Looking further into the future, what will next year’s temperatures be as the next El Niño develops (as predicted by a number of methods, see figure below)?
Figure 5. Set of predictions of ENSO conditions by various models (dynamical and statistical). To be considered an El Niño event, 3-month temperature anomalies must be measured above +0.5°C for 5 consecutive months. Approximately 1/2 of the models are predicting a new El Niño event by the end of this year. The other models predict ENSO-neutral conditions through next spring.
Here, in a sneak peak of my monthly `State of the Poles` post, I wanted to mark a significant event: the area of Arctic sea ice has fallen below the climatological minimum. This occurs with ~6 weeks left in the Arctic melt season. In similar fashion as in other recent years, UIUC data show Arctic sea ice area values at a stunning -2 million sq. km. below the average value for this date in time. Instead of 6.5 million sq. km., today’s value is 4.5 million sq. km., the record lowest for this calendar day. Conditions on the Pacific side of the Arctic sea ice pack (another graphic here) are starting to deteriorate, so rapid melt of additional hundreds of thousands of sq. km. of sea ice could occur in the next month or so. The recorded history yearly minimum sea ice area is ~2.91 million sq. km. Stay tuned for this year’s minimum, which will likely occur in early September.
The National Climate Data Center, in its summary of drought conditions as of the end of June 2012, reported that 55% of the contiguous U.S. was experiencing moderate to extreme drought, as the graphic below shows. This is the largest percentage since December 1956 when 58% of the U.S. experienced similar conditions. The Palmer Drought Index, whose data base goes back 112 years, is relied upon for drought comparisons before 2000.
Figure 1. Drought conditions across the United States as of early July 2012 from the Drought Monitor.
In my last post on drought, I stated, “There’s no widespread crisis to speak of yet, but inhabitants as well as policymakers should monitor conditions as the year progresses.” Well, the NCDC established the case for a widespread crisis with their latest summary, which was not issued until after my post. Crops and livestock are now being negatively affected. The following two charts show corn and soybean prices. The recent peaks are due to worsening conditions across the breadbasket and the USDA’s recent crop downgrade.
Figure 2. Corn (top) and soy (bottom) prices and volume charts for the past 12 months.
1988 was also a very bad year for corn in the U.S. Here is a chart from the USDA comparing 1988 and 2012 corn ratings:
Figure 3. Comparison of corn ratings (good + excellent) as determined by the USDA as of early July 2012.
You can see that conditions in 1988 worsened earlier in the year (solid blue line @30% ~3 weeks before the solid yellow line). It remains to be seen how bad conditions eventually get in 202.
So conditions are the worst since Dec. 1956. How else do today’s conditions compare to earlier droughts? The following graphic from USA Today helps put them in context:
Figure 4. Comparison of extensive drought in U.S. history.
The percentage of the country in moderate to severe drought in June 2012 is the sixth highest since 1900. The 1930s are well known as Dust Bowl years. Conditions aren’t expected to get that bad, even if drought were to dominate the area for the next few years, primarily because of changes in farming practices. Topsoil was easily scoured from the earth in the 1930s and was moved around by winds, sometimes for dozens or hundreds of miles, hence the name ‘Dust Bowl’. The droughts of the mid-1950s were also quite extensive. The U.S. is fortunate that the return period of these conditions was ~55 years.
I’ve also written in my drought posts that the current drought, extensive and intense as it is, is not without historical precedent and that a clear climate change linkage is not available at this time. With generally warmer temperatures and more variable precipitation patterns, one might conclude that drought would be more likely to occur in recent years than in the 1900s. As the USA Today chart shows, that clearly hasn’t happened. The conditions in 2012 are more closely related to the double-dip La Niña that just ended:
Figure 5. Time series of temperature anomalies in the NINO3.4 region. Positive values for 5 consecutive 3-month periods correspond to El Niño events while similar periods with negative values correspond to La Niña events.
This drought is very serious and everybody should treat it as such Part of that statement is acknowledging the lack of a clear anthropogenic climate change signal at this point in time. Conditions aren’t expected to significantly improve in the next couple of weeks. The extent and intensity of drought can expand and worsen within that time. We can also expect higher prices for food starting next year and into 2014 – additional economic headwinds that the U.S. can ill-afford at this time.
The 2012 U.S. heat wave has made considerable news. So none of this should come as any particular shock, perhaps just a little extra shock to what most of us in the U.S. have experienced so far this year. The average temperature for the contiguous U.S. during June was 71.2°F, which is 2.0°F above the 20th century average, which placed June 2012 as the 12th warmest June on record, as the NCDC announced Monday. June 1933 was the warmest June for the U.S. on record due to Dust Bowl conditions. It was also the tenth driest June on record, even with record precipitation in Florida as a result of Tropical Storm Debby. As I wrote earlier, my state of Colorado experienced its warmest June on record. Seven nearby states experienced top-ten warmest Junes.
The Jan-Jun 2012 period is the warmest such period in U.S. history, as the following graphic displays:
Figure 1. The five warmest years for the contiguous U.S. compared to 2012 as of the end of June 2012.
You can see that the first three months of the year were much warmer than average, but it was March that really pushed conditions to an extreme level: +6F. Since then, the year-to-date average anomaly has edged back down to “just” +4.5F. 1998 was the warmest year on record, largely due to the strong 1997-1998 El Nino event. Note that 2006 also makes this list – and that was without the aid of a strong El Nino. 2012 is clearly much more anomalous than any other year to date. The only way it won’t finish as the warmest year on record is if much cooler than normal conditions blanket most of the country for the remainder of the year. It’s not impossible, but conditions would need to be quite different from what we’ve experienced so far this year.
Meteorologists and climatologists look at other time periods that aren’t calendar years. For instance, the past 12 months (Jul 2011 – Jun 2012) just set a new record for the warmest 12-month period on record in the U.S., squeaking past the record that the end of May (Jun 2011 – May 2012) set, as the following graphic shows:
Figure 2. The set of warmest 12-month periods for the contiguous U.S. in the modern-era.
The past 12 months were 3.23F warmer than the long-term average, which is only slightly higher than the 3.18F anomaly for the preceding 12-month period. These two values are both higher than the 2.83F anomaly for the preceding 12-month period (May 2011-April 2012) and the 2.61F anomaly for April 2011-March 2012. Thus, out of the 12 warmest 12 consecutive month periods in contiguous U.S. history, 1/3 of them have occurred in just over the past year. The odds of this occurring randomly is just 1 in 1,594,323. Thus, until 124,652 AD, we should only see one more 13-month period so warm, and that assumes the climate is staying the same as it did during the past 118 years. Needless to say, such an assumption looks incredibly weak.
Looking further at the graph, you can see that 21st century periods dominate the top-12. That is one important difference from the previous graph which showed 1934 and 1921 and the 3rd and 5th warmest years on record. Those years had stretches of time that were shorter than 12 consecutive months over the entire country that were anomalously warm. The heat that is occurring now is spread over a larger area than previous heat waves. Specific heat values for a location or during just one month might not hit record highs, but overall conditions are warmer now than during previous warm periods in the U.S. In other words, the background climate is warmer than it was in 1921 or 1934, enough so that heat records and long stretches of very warm conditions are a little likelier each year to occur.
Another kind of graph might help the reader visualize this:
The CEI: “summariz[es] and present[s] a complex set of multivariate and multidimensional climate changes in the United States so that the results could be easily understood and used in policy decisions made by nonspecialists in the field.” It shows the percentage area of the U.S. with top 10% extremes. Obviously, January-June 2012 set a new record at 44%.
If the planet continues to warm throughout the 21st century, which is more likely to occur the longer we continue emitting heat-trapping greenhouse gases, months, seasons, and years of time that break records today could be considered cool by comparison to conditions at the end of the century. The implications are wide-ranging and profound for human societies and ecosystems. The world won’t end, but it certainly won’t be the same as today either.
