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.
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.
Figure 2. Global temperature anomaly map for March 2013 from NOAA.
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.