According to the NSIDC, sea ice creation during April measured 1.5 million sq. km. This melt rate was approximately normal for the month, so April′s extent remained below average again. Instead of measuring near 15 million sq. km., April 2013′s average extent was only 14.37 million sq. km., a 630,000 sq. km. difference. In terms of annual maximum values, 2013′s 15.13 million sq. km. was 733,000 lower than normal.
Barents Sea (Atlantic side) ice once again fell from its climatological normal value during the month after remaining low during most of the winter. Kara Sea (Atlantic side) ice temporarily recovered from its wintertime low extent and reached normal conditions, which is also different from spring 2012′s conditions, before 2013 melt caused the extent to fall below normal conditions again. The Bering Sea (Pacific side), which saw ice extent growth due to anomalous northerly winds in 2011-2012, saw similar conditions in December 2012 through February 2013. This caused anomalously high ice extent in the Bering Sea again this winter. As it did previously this winter, an extended negative phase of the Arctic Oscillation allowed cold Arctic air to move far southward and brought warmer than normal air to move north over parts of the Arctic. The AO’s tendency toward its negative phase in recent winters is related to the lack of sea ice over the Arctic Ocean in September each fall. Warmer air slows the growth of ice, especially ice thickness. This slow growth allows more melt than normal during the subsequent summer, which helps establish and maintain negative AO phases. This is a destructive annual cycle for Arctic sea ice.
In terms of climatological trends, Arctic sea ice extent in April has decreased by 2.3% per decade, the lowest of any calendar month. This rate is closest to zero in the late winter/early spring months and furthest from zero 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 (much more or less negative) any time soon, but increasingly negative rates are likely in the foreseeable future. Additional low ice seasons will continue. Some years will see less decline than other years (e.g., 2011) – but the multi-decadal trend is clear: 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 have established a new climatological 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.
During April 2013, the Scripps Institution of Oceanography measured an average of 398.35ppm CO2 concentration at their Mauna Loa, Hawai’i’s Observatory.
This value is a big deal. Why? Because not only is 398.35 ppm the largest CO2 concentration value for any April in recorded history, it is the largest CO2 concentration value in any month in recorded history. More on that below. This year’s April value is 1.90 ppm higher than April 2012′s! Month-to-month differences typically range between 1 and 2 ppm. This jump of 1.90 ppm is within that range. It is also ~0.9 ppm less than March’s and 1.47 ppm less than February’s year-over-year change of 3.37 ppm. The unending trend toward higher concentrations with time, no matter the month or specific year-over-year value, as seen in the graphs below, is more significant.
Let’s get back to that all-time high concentration value. The yearly maximum monthly value normally occurs during May. Last year was no different: the 396.78ppm concentration in May 2012 was the highest value reported last year and, prior to the last three months, in recorded history (neglecting proxy data). I expect May of this year to produce another all-time record value. That value will hold first place until February 2014. I wrote the following three months ago:
If we extrapolate last year’s maximum value out in time, it will only be 2 years until Scripps reports 400ppm average concentration for a singular month (likely May 2014; I expect May 2013′s value will be ~398ppm). Note that I previously wrote that this wouldn’t occur until 2015 – this means CO2 concentrations are another climate variable that is increasing faster than experts predicted just a short couple of years ago.
For the most part, I stand by that prediction. But actual concentration increases might prove me wrong. Here is why: the difference in CO2 concentration values between May 2012 and March 2012 was 2.33 ppm (396.78 – 394.45). If we do the simplest thing and add that same difference to this March’s value, we get 399.67 ppm. That is awfully close to 400 ppm, but less than the 399.93 ppm extrapolation I performed in February. It’s also close to the 399.3 ppm extrapolation I calculated in March. I discussed May 2013′s projection with Sourabh after February’s post. They predicted 399.5-400 ppm concentration for May 2013. For the second month in a row, I think NOAA will measure May 2013′s mean concentration near 399.3 ppm.
Figure 1 – Time series of CO2 concentrations measured at Scripp’s Mauna Loa Observatory in April from 1958 through 2013.
CO2Now.org added the `350s` and `400s` to this month’s graphic. I suppose they’re meant to imply concentrations shattered 350 ppm back in the 1980s and are pushing up against 400 ppm now in the 2010s.
How do concentration measurements change in calendar years? The following two graphs demonstrate this.
Figure 2 – Monthly CO2 concentration values from 2009 through 2013 (NOAA). Note the yearly minimum observation is now in the past and we are one month removed from the yearly maximum value. NOAA is likely to measure this year’s maximum value near 399ppm.
Figure 3 – 50 year time series of CO2 concentrations at Mauna Loa Observatory. The red curve represents the seasonal cycle based on monthly average values. The black curve represents the data with the seasonal cycle removed to show the long-term trend. This graph shows the recent and ongoing increase in CO2 concentrations. Remember that as a greenhouse gas, CO2 increases the radiative forcing of the Earth, which increases the amount of energy in our climate system.
In previous posts on this topic, I showed and discussed historical and projected concentrations at this part of the post. I will skip this for now because there is something about this data that I think provides a different context of the same conversation. I saw a graphic last month that I provides useful focus on this topic:
Figure 4 – CO2 concentration (top) and annual average growth rate (bottom). Source: Guardian
The top part of Figure 4 should look familiar – it’s the black line in Figure 3. The bottom part is the annual change in CO2 concentrations. If we fit a line to the data, the line would have a positive slope, which means annual changes are increasing with time. So CO2 concentrations are increasing at an increasing rate – not a good trend with respect to minimizing future warming. In the 1960s, concentrations increased at less than 1 ppm/year (average rate of increase in the bottom graph by decade). In the 2000s, concentrations increased at 2.07 ppm/year. This isn’t surprising – CO2 emissions continue to increase decade after decade. Natural systems are not equipped to remove CO2 emissions quickly from the atmosphere. Indeed, natural systems will take tens of thousands of years to remove the CO2 we emitted in the course of a couple short centuries. Human systems do not yet exist that remove CO2 from any medium (air or water). They are not likely to exist for some time. So NOAA will extend the right side of the above graphs for years and decades to come.
The greenhouse effect details how these increasing concentrations will affect future temperatures. The more GHGs (CO2 and others) are in the atmosphere, all else equal, the more radiative forcing the GHGs cause. More forcing means warmer temperatures as energy is re-radiated back toward the Earth’s surface. Conditions higher in the atmosphere affects this relationship, which is what my volcano post addressed. A number of medium-sized volcanoes injected SO2 into the stratosphere (which is above the troposphere – where we live and our weather occurs) in the last decade. Those SO2 particles reflected incoming solar radiation. This happened because of their chemical and radiative properties. So while we emitted more GHGs into the troposphere, less radiation entered the troposphere (the bottom layer of the atmosphere) in the past 10 years than the previous 10 years. With less incoming radiation, the GHGs re-emitted less energy toward the surface of the Earth. This is likely part of the reason why the global temperature trend leveled off in the 2000s after its relatively rapid run-up in previous decades.
This situation is important for the following reason. Once the SO2 falls out of the atmosphere, the additional incoming radiation will encounter higher GHG concentrations than was present in the late 1990s. As a result, we will likely see a stronger surface temperature response sometime in the future than the response of the 1990s.
The remainder of the reason is the oceans. Thanks to the Interdecadal Pacific Oscillation’s most recent negative phase, the Pacific in particular absorbed heat energy near the surface and transported it to the deep ocean instead of allowing the heat to accumulate near the surface. The following graphic shows how heat absorption by global oceans changed in recent years:
Figure 5. New research that shows anomalous ocean heat energy locations since the late 1950s. The purple lines in the graph show how the heat content of the whole ocean has changed over the past five decades. The blue lines represent only the top 700 m and the grey lines are just the top 300 m. Source: Balmaseda et al., (2013)
This temporary energy transport to the deep ocean is good news in the short-term: global surface temperatures slowed their rise during the 2000s compared to the 1990s and 1980s. That does not mean however the global warming has stopped, as ideological skeptics want you to believe. That heat energy still exists in the Earth’s climate system. The oceans move heat around the planet just as the atmosphere does. The very large amount of extra heat currently in the deep ocean will eventually come back up to the surface. When it does, it add to the surface warming signal. So we can expect to see an extra rise of global mean surface temperatures sometime in the future. Thus, this is not good news in the long-term.
The rise in CO2 concentrations will slow down, stop, and reverse when we decide it will. It depends primarily on the rate at which we emit CO2 into the atmosphere. We can choose 350 ppm or 450 ppm or any other target. That choice is dependent on the type of policies we decide to implement. It is our current policy to burn fossil fuels because we think doing so is cheap, albeit inefficient and without proper market signals. We will widely deploy clean sources of energy when they are cheap, the timing of which we control. We will remove CO2 from the atmosphere when we have cheap and effective technologies and mechanisms to do so, which we also control. These future trends depend on today’s innovation and investment in research, development, and deployment. Today’s carbon markets are not the correct mechanism, as they are aptly demonstrating. We will limit future warming and climate effects when we choose to do so.
During the month of April 2013, Denver, CO (link updated monthly) recorded a 74°F difference between maximum and minimum temperatures. This fact tells us nothing about how temperatures compare to climatological norms however. For the entire month, Denver was 5.7°F below normal (41.7°F vs. 46.4°F). The maximum temperature of 80°F was recorded on the 29th while the minimum temperature of 6°F was recorded on the 10th. Here is the time series of Denver temperatures in April 2013:
Figure 1. Time series of temperature at Denver, CO during April 2013. Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]
But it also got me to thinking about the difference between spring 2013 and spring 2012. As many of us remember, temperatures in the US in 2012 were very warm compared to climatological norms. So how different were temperatures in Denver in February-March-April 2013 versus 2012? I decided to take a look. Let’s start with extending the dates in Figure 1 back to the beginning of February 2013:
Figure 2. Time series of temperature at Denver, CO during February-April 2013. Daily high temperatures are in red, daily low temperatures are in blue, climatological normal (1981-2010) high temperatures are the top dark gray line, and normal low temperatures are the bottom dark gray line. [Source: NWS]
This graphic simply demonstrates the same story that I wrote above as well as in my March and February Denver Climate Summary posts. February was obviously colder than normal due to extended cold air masses over the area. March and April were also colder than normal, but this was due to vigorous mid-latitude cyclones that brought Arctic air masses south over the area. This is evident by the significant dips in both maximum and minimum daily temperatures: there was one in the beginning of March, another in the end of March, and three in April.
With this chart in mind, let’s look at the difference between 2012 and 2013. First, daily maximum temperatures:
Figure 3. Time series of maximum temperature at Denver, CO during February-April 2012 and 2013. 2013 temperatures are in brick-red, 2012 temperatures are in red, and climatological normal (1981-2010) high temperatures are the dark gray line with green crosses. [Source: NWS]
My memory of 2012′s maximum temperatures was close to reality. February 2012 was colder than I remember, but this was likely affected by the warmth of April 2012 and the record-setting daily highs in the summer of 2012. Figure 3 shows a very large difference between daily maximum temperatures in 2012 and 2013, especially after the 22nd of March. I didn’t remember the cold snap on April 3, 2012. This graphic shows, by proxy, the lack of spring synoptic storms in 2012. Daily maximum temperatures rarely fell below the normal for the date. Instead, April temperatures were as much as 20°F warmer than normal on some dates, but regularly 10°F warmer than normal. In contrast, 2013 temperatures were often 25-30°F colder than normal. The difference between two years’ temperatures is a measure of interannual weather variability. I have more on that below.
Figure 4. Time series of minimum temperature at Denver, CO during February-April 2012 and 2013. 2013 temperatures are in blue, 2012 temperatures are in green, and climatological normal (1981-2010) high temperatures are the dark gray line with brown pluses. [Source: NWS]
Again, February 2012′s temperatures were similar to February 2013′s. The specific dates of temperature swings obviously varies between the two years. March 2012 and March 2013 also look similar, up until the 22nd of March (see maximum temperatures above also). Thereafter, the time series diverge with much colder air in place over Denver four different times through the end of April. 2012 had warmer than normal minimum temperatures through most of April. The combination of warmer than normal nights and days, combined with a relative lack of precipitation in 2012 set the stage for the record-setting warmth in the summer as well as the rapid decline in drought conditions, which are still largely present now.
Interannual Variability
I have written hundreds of posts on the effects of global warming and the evidence within the temperature signal of climate change effects. This series of posts takes a very different look at conditions. Instead of multi-decadal trends, this series looks at highly variable weather effects on a very local scale. The interannual variability I’ve shown above is a part of natural change. Climate change influences this natural change – on long time frames. The climate signal is not apparent in these figures because they are of too short duration. The climate signal is instead apparent in the “normals” calculation, which NOAA updates every ten years. The most recent “normal” values cover 1981-2010. The temperature values of 1981-2000 are warmer than the 1971-2000 values, which are warmer than the 1961-1990 values. The interannual variability shown in the figures above will become a part of the 1991-2020 through 2011-2040 normals.
Precipitation
Precipitation was above normal again during April 2013, extending this new trend to three months. During the month, 1.87″ of liquid water equivalent precipitation fell, compared to 1.71″ normally. The wettest April on record was in 1983 when 4.56″ of precipitation fell. There were three notable weather events during April: a 6″+ snowstorm on the 9th, a 7″+ snowstorm on the 15th, and a 5″+ snowstorm on the 22nd. In total, the NWS recorded 20.4″ of snow.
I could write a dissertation on this topic and spend the rest of my life researching and publishing on it. I will have to settle for a short blog post for now, because my own research is in need of my attention.
People posted a number of tweets and articles on how “Political ideology affects energy-efficiency attitudes and choices“, which is the title of a new PNAS article. The upshot: ideology trumps the free market. This isn’t a surprise to me anymore – I’ve studied plenty of cases in the past two years that demonstrate this phenomenon. In this case, peoples’ purchases of energy-efficient light bulbs were most influenced by what the bulb’s labeling stated. The study made two stickers available: “Protect the Environment” or blank. In both cases, the researchers made the same bulb benefits (energy use & cost) available to each potential purchaser. The only difference was the presence of a blank or pro-environment sticker on the packaging. With the pro-environmental sticker, conservatives were less likely to purchase the CFL bulb. Without it, conservatives and liberals were equally likely to purchase the CFL bulb. That’s not rational, which is a significant assumption of modern economic theory. The result shows, unsurprisingly, that peoples’ behavior depends on their personal ideology and value system. This has obvious implications for climate change activists: you have to operate in the value system of your targeted audience if you want them to receive your proposals well. Beating the same drums harder won’t make conservatives care about climate change.
Climate groups are willfully failing elsewhere. A new Yale Project on Climate Change Communication and George Mason University Center for Climate Change Communication poll demonstrates that increasing numbers of Americans are drawing incorrect conclusions from recent weather events to climate change. The warmest year on record in the US (2012) was made more severe due to global warming, according to 50% of respondents. A similar number believe the ongoing US drought is worse due to global warming. The results go on and on.
Here is the rub: these beliefs have no basis in scientific fact. 2012 US temperatures were largely influenced by natural interannual variability. It was warmer than 1998 by more than 1°F, which is significant. But identifying a global warming signal in one year’s temperature data for the US is beyond the current capabilities of science. We can say more robustly that the 2000s were significantly warmer than the 1990s, which were warmer than the 1980s, etc. 2012′s temperatures were extreme and it had implications that are still being felt by human and ecological systems. The important point there is this: are existing systems capable of handling today’s weather extremes? If not, we should do something.
The belief in climate change enhanced drought is also unsupported, as I wrote about a couple of weeks ago. Initial findings from a NOAA-led team were unable to detect a global warming-related signal in either the onset, magnitude, or extent of the extraordinary 2012 drought. This isn’t particularly surprising when you consider the last two droughts of similar extent and severity occurred in the 1950s and 1930s – prior to much anthropogenic forcing. Specifically, they found that “The interpretation is of an event resulting largely from internal atmospheric variability having limited long lead predictability.” Again, this drought is producing effects, but it isn’t directly attributable to climate change. The question remains: are existing systems capable of handling these types of extreme events? If they aren’t, we should do something about them, not draw unscientific causal linkages in an effort to build support for change.
The IPCC’s SREX report (Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation), issued just last year, reinforces this message. There is a detectable global warming signal in a few measurable parameters such as temperature, water vapor, and sea level change. But the climate system retains a great deal of natural variability which scientists do not fully understand. Climate conditions will change in the next 90 years, but the likelihood of those changes varies. Weather conditions may or may not change. Their inherent transience makes it difficult to ascribe causal factors behind any changes. Note further that climate projections of the 2090s are not climate conditions of the 2090s or 2010s. Identifying likely future changes does not translate to detecting those changes today.
Yale and George Mason should digest their poll results along with the latest guidance from scientific peer-reviewed literature to help guide their communication efforts moving forward. Given the results of this latest poll, they have their work cut out for them. Framing, whether it is related to selling CFLs to a diverse public or differentiating between weather and climate, is critically important in climate communication.
According to the Drought Monitor, drought conditions improved recently across some of the US. As of Mar. 12, 2013, 47.3% of the contiguous US is experiencing moderate or worse drought (D1-D4) as the 2011-2012 drought extended well into 2013. That is the lowest percentage in a number of months. The percentage area experiencing extreme to exceptional drought increased from 14.6% to 14.7%, but this is ~3% lower than it was three months ago. Percentage areas experiencing drought across the West decreased in the past month as a series of late season cyclones impacted the region. Drought across the Southwest worsened slightly while rain from storms maintained the low-level of drought conditions in the Southeast.
My previous post preceded the series of major winter storm that affected much of the US. In some places in the High Plains and Midwest, 12″ or more of snow fell. With relatively high liquid water equivalency, each storm dropped almost ~1″ of water precipitation, of which the area was in sore need. Unfortunately, these same areas required 2-4″ of rain to break their long-term drought. In other words, while welcome, recent snows have reduced the magnitude of the drought in many areas, but have not completely alleviated them. Ironically, a very different problem arose from these storms: flooding.
Figure 1 – US Drought Monitor map of drought conditions as of April 25th.
If we focus in on the West, we can see recent shifts in drought categories:
Figure 2 – US Drought Monitor map of drought conditions in Western US as of April 25th.
Some relief is evident in the past month (see table on left), including some changes in the mountains as storms recently dumped snow across the region. Mountainous areas and river basins will have to wait until spring for snowmelt to significantly alleviate drought conditions. As you can probably tell, this is a large area experiencing abnormally dry conditions for about one year now.
Here are conditions for Colorado:
Figure 3 – US Drought Monitor map of drought conditions in Colorado as of April 25th.
There is some evidence of relief evident over the past three months here. Instead of 100% of the state in Severe drought, only 78% is today. The central & northern mountains, as well as the northern Front Range (Denver north to the border) enjoyed the most relief since February. The percentage area in Extreme drought also dropped significantly from 59% to 38%. Exceptional drought shifted in space from northeastern Colorado to central Colorado while southeastern Colorado remained very dry.
Drought conditions improved somewhat across the southwestern portion of the state in the past couple of weeks. The percentage area that is experiencing less than Severe drought conditions continues to track downward, which is a good sign. Unfortunately, Exceptional drought conditions continued their hold over the eastern plains.
Here are conditions for the High Plains states:
Figure 4 – US Drought Monitor map of drought conditions in the High Plains as of April 25th.
The large storms that moved over this area in the past month reduced the worst drought conditions across Nebraska, South Dakota, and Wyoming. The percentage area with Exceptional drought dropped from 27% to 7%; Extreme drought dropped from 61% to 28%; and Severe drought dropped from 87% to 70%.
With rather significant areas still experiencing moderate or worse drought across much of the US west of the Mississippi River, drought remains a serious concern in 2013. I previously hypothesized that much of the 2012 drought was partly a result of natural climate variability and underlying long-term warming. I wrote about NOAA’s examination into the causes of the 2012 drought a couple of weeks ago in which the authors suggested it was not heavily influenced by long-term warming.
US drought conditions are more influenced by Pacific and Atlantic sea surface temperature conditions. Different natural oscillation phases preferentially condition environments for drought. Droughts in the West tend to occur during the cool phases of the Interdecadal Pacific Oscillation and the El Niño-Southern Oscillation, for instance. Beyond that, drought controls remain a significant unknown. Population growth in the West in the 21st century means scientists and policymakers need to better understand what conditions are likeliest to generate multidecadal droughts, as have occurred in the past.
As drought affects regions differentially, our policy responses vary. A growing number of water utilities recognize the need for a proactive mindset with respect to drought impacts. The last thing they want is their reliability to suffer. Americans are privileged in that clean, fresh water flows when they turn their tap. Crops continue to show up at their local stores despite terrible conditions in many areas of their own nation (albeit at a higher price, as we will find this year). Power utilities continue to provide hydroelectric-generated energy.
That last point will change in a warming and drying future. Regulations that limit the temperature of water discharged by power plants exist. Generally warmer climate conditions include warmer river and lake water today than what existed 30 years ago. Warmer water going into a plant either means warmer water out or a longer time spent in the plant, which reduces the amount of energy the plant can produce. Alternatively, we can continue to generate the same amount of power if we are willing to sacrifice ecosystems which depend on a very narrow range of water temperatures. As with other facets of climate change, technological innovation can help increase plant efficiency. I think innovation remains our best hope to minimize the number and magnitude of climate change impacts on human and ecological systems.
I spent a lot of time on record temperatures in Colorado in 2012 – they were all record highs. Due to annual weather variability, there are a couple of different records in April 2013: record lows. There have been four record lows set or tied in Denver, CO this April:
Needless to say, with record low temperatures due to vigorous synoptic cyclones that brought Arctic air masses down into the middle of the country, April’s average temperature is among the lowest on record. I will have more to say about that next week after the month ends. Denver may not record a bottom-10 moth because much more seasonable weather is on tap for the next week. In contrast, two record highs were set in April 2012: 84F on the 1st and 88F on the 24th.
In other news, Boulder, CO set a monthly record for snowfall: 47.4″ through the 23rd! The old record of 44″ was set in 1957. The official snowfall measurement site for Denver (Denver Int’l Airport) recorded “only” 20.4″ of snow for the month-to-date. With 60F+ temperatures forecasted from today through next Tuesday, DIA won’t challenge the top-10 snowiest Aprils (#10 recorded 21.0″ of snow).
Remember that one month’s, season’s or year’s temperatures, precipitation, or even drought are not indicative by themselves of climate change. They are too heavily influenced by individual weather systems. When I discuss climate change, I write about long-term trends (decadal to multi-decadal). Natural variability influences individual weather events that overlie the long-term climate signal. I’ve written before that climate change means we are more likely to see record high temperatures than record low temperatures. The weather will continue to set both, but will set the former at a higher rate moving forward than the latter. Of course, I for one am very glad there was more precipitation than normal for April. Last year’s drought and record hot summer was not enjoyable to live through. Denver-Boulder and the surrounding region will unfortunately need months in a row of above average precipitation to break the long-term drought. This spring’s precipitation pattern slightly reduced the intensity and areal coverage of drought. I will update my last drought post in the next couple of days.
According to data released by NOAA, March was the 10th warmest globally on record. Here are the NOAA data and report. NASA also released their suite of graphics, but their surface temperature data page is down today, so I cannot relay how NASA’s March temperature compares to historical Marches. Once their site is back up, I will update this post. [Update: NASA's analysis resulted in their 9th warmest March on record. Here are the data for NASA’s analysis.] 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 two techniques provide a check on one another and confidence for us.
The details:
March’s global average temperatures were 0.59°C (1.062°F) above normal (1951-1980), according to NASA, as the following graphic shows. The past three months have a +0.57°C temperature anomaly. And the latest 12-month period (Apr 2012 – Mar 2013) had a +0.60°C temperature anomaly. The time series graph in the lower-right quadrant shows NASA’s 12-month running mean temperature index. The recent downturn (2010-2012) was largely due to the latest La Niña event (see below for more) that ended early last summer. Since then, ENSO conditions returned to a neutral state (neither La Niña nor El Niñ0). Therefore, as previous anomalously cool months fall off the back of the running mean, and barring another La Niña, the 12-month temperature trace should track upward again throughout 2013.
Figure 1. Global mean surface temperature anomaly maps and 12-month running mean time series through March 2013 from NASA.
According to NOAA, March’s global average temperatures were 0.58°C (1.044°F) above the 20th century mean of 12.7°C (54.9°F). NOAA’s global temperature anomaly map for March (duplicated below) shows where conditions were warmer than average during the month.
The two different analyses’ importance is also shown by the preceding two figures. Despite small differences in specific global temperature anomalies, both analyses picked up on the same temperature patterns and their relative strength.
The very warm conditions found over Greenland are a concern. Greenland was warmer than average during more months in recent history than not. In contrast to 2012, northern Eurasian temperatures were much cooler than normal. This is likely a temporary, seasonal effect. Long-term temperatures over much of this region continue to rise at among the fastest rate for any region on Earth.
The NASA and NOAA surface temperature maps correlate well with the 500-mb height pressure anomalies, as seen in this graph:
Figure 3. 500-mb heights (white contours) and anomalies (m; color contours) during March 2013.
Note the correspondence between the height map and the NASA & NOAA surface temperature maps: lower heights (negative height anomalies) present over the North Atlantic and northern Eurasia overlay the cold surface temperature anomalies at the surface. Similarly, warm surface temperature anomalies are located under the positive 500-mb height anomalies.
These temperature observations are of interest for the following reason: the globe came out of a moderate La Niña event in the first half of last year. During the second half of the 2012 and the first part of 2013, we remained in a ENSO-neutral state (neither El Niño nor La Niña):
The last La Niña event hit its highest (most negative) magnitude more than once between November 2011 and February 2012. Since then, tropical Pacific sea-surface temperatures peaked at +0.8 (y-axis) in September 2012. 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 2010 (when the globe reached record warmth) to 2012. So a natural, low-frequency climate oscillation affected the globe’s temperatures during the past couple of years. Underlying that oscillation is the background warming caused by humans. And yet temperatures were still in the top-10 warmest for a calendar year (2012) and individual months, including March 2013, in recorded history.
Skeptics have pointed out that warming has “stopped” in recent years (by comparing recent temperatures to the 1998 maximum which was heavily influenced by a strong El Niño even), which they hope will introduce confusion to the public on this topic. What is likely going on is quite different: a global annual energy imbalance exists (less outgoing energy than incoming energy). If the surface temperature rise has seemingly stalled, the excess energy is going somewhere. That somewhere is likely the oceans, and specifically the deep ocean (see the figures below). Before we all cheer about this (since few people want surface temperatures to continue to rise quickly), consider the implications. If you add heat to a material, it expands. The ocean is no different; sea-levels are rising in part because of heat added to it in the past. The heat that has entered in recent years won’t manifest as sea-level rise for some time, but it will happen. Moreover, when the heated ocean comes back up to the surface, that heat will then be released to the atmosphere, which will raise surface temperatures as well as introduce additional water vapor. Thus, the short-term warming rate might have slowed down, but we have locked in future warming (higher future warming rate) as well as future climate effects.
Figure 5. Total global heat content anomaly from 1950-2004. An overwhelming majority of energy went to the global oceans.
Figure 6. New research that shows anomalous ocean heat energy location since the late 1950s. The purple lines in the graph show how the heat content of the whole ocean has changed over the past five decades. The blue lines represent only the top 700 m and the grey lines are just the top 300 m. Source: Balmaseda et al., (2013)
Balmaseda et al.’s work demonstrates the transport of anomalous energy through the depth of the global oceans. Note that the grey lines’ lack of significant change from 2004-2008 (upper 300m). Observations of surface temperature include the very top part of this 300m layer. Since the layer hasn’t changed much, neither have surface temperature readings. Note the rapid increase in heat content within the top 700m. Given the lack of increase in the top 300m, the 300-700m layer heat content must have increased. By the same logic, the rapid growth in heat content throughout the depth of the ocean, which did not stall post-2004, provides evidence for anomalous heat location. You can also see the impact of major volcanic eruptions on ocean heat content: less incoming solar radiation means less absorbed heat.
A significant question for climate scientists is this: are climate models capable of picking up this heat anomaly signal and do they show a similar trend? If they aren’t, then their projections of surface temperature change is likely to be incorrect since the heat is warming the abyssal ocean and not the land and atmosphere in the 2000s and 2010s. If they aren’t, climate policy is also impacted. Instead of warmer surface temperatures (and effects on drought, agriculture, and health to name just a few), anomalous ocean heat content will impact coastal communities more than previously thought. Consider the implications of that in addition to the AR4′s lack of consideration of land-based ice melt: sea level projections could be too conservative.
That said, it is also a fair question to ask whether today’s climate policies are sufficient for today’s climate. In many cases, I would say they aren’t sufficient. Paying for recovery from seemingly localized severe weather and climate events is and always will be more expensive than paying to increase resilience from those events. As drought continues to impact US agriculture, as Arctic ice continues to melt to new record lows, as storms come ashore and impacts communities that are not prepared for today’s high-risk events (due mostly to poor zoning and destruction of natural protections), economic costs will accumulate in this and in future decades. It is up to us how many costs we subject ourselves to.
As President Obama began his second term with climate change “a priority”, he tosses aside the most effective tool available and most recommended by economists: a carbon tax. Every other policy tool will be less effective than a Pigouvian tax at minimizing the actions that cause future economic harm. It is up to the citizens of this country, and others, to take the lead on this topic. We have to demand common sense actions that will actually make a difference. But be forewarned: even if we take action today, we will still see more warmest La Niña years, more warmest El Niño years, more drought, higher sea levels, increased ocean acidification, more plant stress, and more ecosystem stress. The biggest difference between efforts in the 1980s and 1990s to scrub sulfur and CFC emissions and future efforts to reduce CO2 emissions is this: the first two yielded an almost immediate result while it will take decades before CO2 emission reductions produce tangible results humans can see.
