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.
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.
Abram et al.‘s Figure 5| Melt response over the past millennium. a, Schematic of Prince Gustav ice shelf history showing its presence (blue), intervals of rapid retreat (1957 and 1989; yellow) and collapse (1995; red). b,c, JRI mean temperature anomaly (green;b) and melt percentage (red;c) shown as 11-year moving averages. Thick lines are 21-year Gaussian kernel filters; dashed lines denote 1981–2000 mean. Lowest temperatures and melt occurred at AD 1410–1460, followed by progressive warming and a nonlinear melt increase. d, The occurrence of melt layers (grey lines) and a 100-year stepped average of melt frequency (purple) at Siple Dome in West Antarctica.
New research published in Nature Geoscience from Nerilie J. Abram et al. (subs. req’d) presents evidence that West Antarctic ice melt accelerated over the course of the last 1,000 years. About 400 years ago, average temperature anomalies (based off the 1981-2000 mean) increased from -1°C to -0.75°C (green curve in above graphic). You can see the interannual and interdecadal variability in this time period, which was natural. Then, starting 100 years ago, temperature anomalies rose from -0.75°C to today’s slightly positive anomaly. As a result, the melt percentage jumped to 5% at James Ross Island. That melt jump was nonlinear due to the ~0C melt threshold. As the authors state, “where summer temperatures do exceed the melting threshold, the amount of melt produced is proportional to the sum of the daily positive temperatures rather than their mean. This means that as average summer temperature increases and positive temperature days become warmer and more frequent, the amount of melt produced will exhibit an exponential increase”.
That cause-and-effect relationship is one reason why a 3°C average temperature rise carries so much more impact than a 2°C average temperature rise in polar regions. It also explains why small changes in historical temperatures allowed the ice shelves to form in the first place. The large “permanent” ice shelf collapses in recent history are the effect of rising temperatures. It should be obvious too that predicting the timing of future ice shelf collapses is difficult if not impossible.
The Wilkins Ice Shelf collapsed suddenly in 2009. This shelf is located southwest of the James Ross Island site cited above. As I wrote in the Wilkins post, six other shelves completely collapsed in contemporary times: Prince Gustav Channel, Larsen Inlet, Larsen A, Larsen B, Wordie, Muller and the Jones Ice Shelf. These ice shelves responded to the West Antarctic Ice Sheet (WAIS) warming observed in the last century or so. WAIS warming is occurring faster than almost any other location on the globe. There are areas in the Arctic and now the Antarctic that have observed +2.4°C warming from 1958 through 2009. In addition to anthropogenic near-surface temperature rise, the ocean surrounding Antarctica has warmed recently. Ice shelves are therefore being melted from above as well as below. Does the following sound familiar? “Over the past 18 years, Martinson and his colleagues have measured the physical properties of the ocean around Antarctica and came to the startling conclusion that the majority of the heat anomalies they have measured have occurred since 1960. Unfortunately, those anomalies have been growing exponentially ever since.”
Additional coverage of this paper can be found here and here. [h/t Martin Lack for the HuffPo link]
Based on the above, we know that West Antarctica is warming very rapidly. We know that warming anomalies are growing exponentially. Problematically, even small temperature changes cause exponential changes in melt. Exponential change growing off of exponential change creates a highly nonlinear, and therefore very unpredictable system. What might that mean for the WAIS? It could mean that rapid effects take place in the future. In other words, ice sheet properties could change quickly. Large melt areas could start one day without very little prior signal. Additional ice sheet collapses could take place without much notice. Increasing greenhouse gas emissions will cause increasing radiative forcing, which in turn will cause increased heat storage by some climate component (primarily the ocean to date, but also the atmosphere). Current global energy imbalance guarantees decades’ worth of additional heating. That heat will eventually impact Antarctica and its massive ice sheet. Melting of global land-based ice to date increased global sea level by an average of 8 inches in the last 100 years. If the entire West Antarctic Ice Sheet melted (which would happen sooner than East Antarctica because it rests on bedrock below sea level), sea levels would rise 4.8 meters. The entire WAIS won’t melt for centuries, but sea levels would easily rise more quickly than the current 3mm/yr as annual WAIS melt increases due to increasing temperatures.
There is no catastrophe knocking on the door today, but WAIS melt will affect coastal regions this century. Total sea level rise off the east coast of the US exceeded the global average, which has already caused communities to re-examine infrastructure. Higher levees and other protective structures either have been built or are being considered by cities such as Washington, D.C., Norfolk, and New York City. Efforts to date haven’t been sufficient (see Hurricane Sandy damage along the New Jersey shore), which points to a need for more aggressive analysis of needs and implementation of new climate-based policies. Costs to these and other communities will grow as international mitigation efforts stall.
A team of atmospheric scientists, led by the National Oceanic and Atmospheric Association, issued a report this week that presented initial results of an examination into the extreme 2012 US drought. Its core finding was the drought likely resulted mostly from natural variability. Any climate change signal is relatively small but likely made conditions across the Midwest US a little dryer and a little warmer than they otherwise would have been absent climate change.
The 2012 drought did not grow out of the 2010-2011 Southern drought that impacted Texas and Oklahoma, as many, including myself, theorized as the drought developed. Instead, a stubborn ridge of high pressure took hold over the Plains, which cut off the vital Gulf of Mexico water supply upon which the region depends for agriculture.
This sentence, in the Executive Summary, is key: “The interpretation is of an event resulting largely from internal atmospheric variability having limited long lead predictability.” Many people think severe weather events should be easy to forecast, but the opposite is true. The rarer the event, the more difficult it is to accurately forecast with any kind of time difference. Additionally, the connection to low-frequency climate oscillations (i.e., La Niña: “the 2012 drought occurred in concert with an appreciably warmer ocean in most basins than was the case for any prior historical drought”) were minimal in the 2012 drought, contrary to what I have theorized. That’s the beauty of science, of course. You can be incorrect about something and demonstrate as such when data are analyzed.
Recently, some folks have characterized this event as a “flash drought”, owing to the sudden onset of such an event, as the first graphic below shows. The term obviously borrows from the better known “flash flood” concept. Unlike a flood however, droughts have longer-term impacts on human and ecosystems. Costs are still only estimated at this time (because the drought is ongoing) at $12 billion. While significant, the 1980 drought event that caused 56 billion (2012$) and the 1988 drought that caused 78 billion (2012$) of damages eclipsed the 2012 event (so far). The $12 billion figure is likely to grow as the drought impacts water supply reductions and livestock. The 2012 crop yield deficit was the greatest since 1866.
Figure 1 – U.S. Drought Monitor maps showing the evolution of the 2012 “flash drought” across the US Great Plains. Little evidence existed in November 2011 or even May 2012 that the drought would achieve the extent and intensity that it did.
The drought was the worst on record for WY, CO, NE, KS, MO, and IA, as the following graphic shows. The region experienced a 53% rainfall deficit (39.3mm vs. 73.5mm) in 2012. 1934 held the previous record of -28.4mm deficit. The 2012 deficit corresponds to a 2.7 standardized deficit, which approaches a 1-in-100 event. This relates well to the precipitation time series in the graph below.
Figure 2 – Precipitation and temperature departures from normal for the six states impacted by the 2012 drought. Note the extreme minimum in precipitation on the right side of the top graph. 2012 temperatures as a whole were not as extreme as those recorded twice during the 1930s, but July 2012 still ranks as the warmest month on record for the six states as well as the entire US.
The analysis also suggests that we should not expect similar 2013 precipitation anomalies on the basis of 2012 anomalies alone (based on the report’s Figures 10 and 11). Put another way, just because 2012 was drier than normal, 2013 shouldn’t automatically be drier also. Dry epochs occurred in this region before: in the 1930s and 1950s. Subsequent dry years occurred then due to longer-term changes in natural variability as well as land use practices. The currently is no indication that the 2010s will similarly be a dry epoch. As with the 2012 drought, such a prediction remains beyond current skill.
The diagnosed linkage to low-frequency forcing is interesting. Warm tropical sea-surface temperatures (SSTs) in the Indo-West Pacific Oceans and cold east Pacific conditions tend to dry the mid-latitudes in the winter/spring season and not the summer season. As the first graphic demonstrates, the 2012 drought flashed in the summer and not the winter. So despite primed conditions for drying in winter 2011-12, the Great Plains drought occurred for different reasons.
Of further interest to the future is the following graphs. The researchers generated a 20-member NCAR CAM-4 ensemble with monthly varying SSTs, sea ice, and specified external radiative forcings consisting of greenhouse gases (e.g. CO2, CH4, NO2, O3, CFCs), aerosols, solar, and volcanic aerosols via observations through 2005 and then an emission scenario thereafter (RCP6.0, a moderate emissions scenario pathway developed for the upcoming IPCC’s AR5).
Figure 3 – Model results of the 1996-2012 precipitation minus the 1979-1995 precipitation.
The NCAR CAM4 model might be representing the actual climate well for this time period. Left unsaid in the report is any analysis of the model’s future projections. Other model studies suggest that the central US could experience 2012-type temperature and precipitation conditions more regularly by the end of the 21st century.
Figure 4 – Model probability density functions of precipitation deficits for the six study states.
This figure suggests that the latter half of the time period (1996-2012) modeled had a higher probability of being drier than did the former half (1979-1995). The report did not present a potential cause for this shift in probability. If this probability does not revert back to the 1979-1995 distribution, dry conditions could become a more regular feature of future years.
Figure 5 – Model probability density functions of precipitation surpluses for the six study states.
This figure is not the logical companion to the previous figure. The probability of being wetter and drier could increase if the overall probability density function existed in a certain way. This is not the case however. Instead, the probability of the six states experiencing wetter conditions in the second half of the period studied decreased with respect to the first half.
This report is useful in diagnosing what happened prior to and during the 2012 US drought and in trying to ascertain how predictable such an event might have been. There is considerable interest in accurately predicting this type of event well in advance so as to prepare those who might be affected. This capability remains beyond us for now since this event was primarily driven by natural variability enhanced slightly by underlying change. With climate model projection studies indicating a much warmer and somewhat drier future for this region, stakeholders will likely have to adapt farming and ranching practices. Similarly, municipalities will have to prepare for extremely dry years in their infrastructure planning and practices. Of course, future change could be reduced as a result of our efforts to mitigate anthropogenic forcing. The scale of that endeavor is much larger than most people are aware and thus not likely to take place any time soon. Climate and energy policies need significant revamping at all levels.
According to the NSIDC, weather conditions once again caused less freezing to occur on the Atlantic side of the Arctic Ocean and more freezing on the Pacific side than normal this winter. Similar conditions occurred during the past six boreal winters. Sea ice creation during February measured 766,000 sq. km. Despite this rather rapid growth (38% higher than normal), February′s extent remained well below average for the month. Instead of measuring near 15.64 million sq. km., February 2013′s average extent was only 14.66 million sq. km., a 980,000 sq. km. difference! The Arctic likely reached its maximum annual extent about 10 days ago. In terms of annual maximum values, 2013′s 15.13 million sq. km. was 733,000 lower than normal.February’s relatively high rate of ice formation for February related to the lack of existing sea ice at the beginning of the month. Without ice already in the Ocean, new ice formed as winter continued.
Barents Sea (Atlantic side) ice finally edged toward its climatological normal value during the month after remaining low this winter, as it did in the past 10 winters. Kara Sea (Atlantic side) ice recovered from low extent the past couple of months, which is different from February 2012′s conditions. 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, a 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.
In terms of climatological trends, Arctic sea ice extent in February has decreased by 2.9% 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.
Arctic Pictures and Graphs
The following graphic is a satellite representation of Arctic ice as of February 11, 2013:
As is normal for this time of year, there is not a large difference between these two graphics. Any differences are primarily due to storm systems’ presence that push ice around, or the lack thereof. The lack of sea ice in the Barents Sea (north of Europe) is problematic because wind and ocean currents typically pile sea ice up on the Atlantic side of the Arctic. Sea ice presence in the Bering Sea (between Alaska and Russia) does not alleviate this problem because currents take ice from that area and transport it into the Arctic and then out into the Atlantic. The sea ice on the Atlantic side would be among the first that currents transport and then melt during the spring. With sea ice missing on the Atlantic side, currents will more easily transport Arctic sea ice to southern latitudes where it melts.
Many people questioned the overall health of the Arctic ice pack earlier this month when images (like the one below) and video documented extensive cracks in the ice in the Chukchi and Beaufort Seas. A fellow blogger (and new author!) emailed me about this phenomenon and I wrote that I would blog my thoughts on the topic. As Andrew Freedman wrote, “According to the National Snow and Ice Data Center (NSIDC) in Boulder, Colo., this fracturing event appears to be related to a storm that passed over the North Pole on Feb. 8, 2013, creating strong off-shore ice motion. The event is unusual but not unheard of, as similar patterns were seen in early 2011 and 2008. However, the NSIDC said the fracturing this time is more extensive.” The worry is the extent and size of the cracks and leads as well as the early calendar date at which they are all appearing – up to weeks before normal.
I found this article on the topic and agree with Greg Laden, the author. The cracks and leads might be a big deal or they might not. We will have to wait until the minimum sea ice extent occurs in September before we issue judgment. The scientifically sound course of action would be to wait until early cracks appeared in multiple seasons and then see what the range of response later in the year is. For all we know, the cracks could allow for even more ice to form in March than normal and delay the onset of melting. It strikes me as scientifically unsound and even irresponsible to conjecture about the existence and effect of processes, which we do not understand well. If scientists crow about upcoming devastating Arctic sea ice loss this year and reality doesn’t conform to their wishes, how much credibility with the public do they engender? I think observers should stay patient and discuss the phenomena and effects we do understand – there is plenty of material with which to work!
Figure 3 – NOAA AVHRR infrared picture of Arctic sea ice on 20130312.
The following graph of Arctic ice volume from the end of February demonstrates:
Figure 4 – PIOMAS Arctic sea ice volume time series through February 2013.
As the graph shows, volume (length*width*height) hit another record minimum in June 2012. Moreover, the volume remains far from normal since it just returned to the -2 standard deviation envelope (light gray). I understand that most readers don’t have an excellent handle on statistics, but conditions between -1 and -2 standard deviations are rare and 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 (you have a better chance of winning the Powerball than this). 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 the ice volume anomaly returned to near the -1 standard deviation envelope in early 2011, early 2012, and now early 2013. In each of the previous two years, volume fell rapidly outside of the -2 standard deviation area with the return of summer. That means that natural conditions are not the likely cause; rather, another cause is much more likely to be responsible for this behavior: human influence.
Arctic Sea Ice Extent
Take a look at February’s areal extent time series data:
Figure 5 – NSIDC Arctic sea ice extent time series through late March 2013 compared with last five years’ data and climatological norm (dark gray line) and standard deviation envelope (light gray).
As you can see, this year’s extent (light blue cuve) grew more rapidly in December than February. This graph also shows that this year’s extent remained at historically low levels through the winter, well below average values (thick gray curve), just as it did in the previous five winters, which are also shown on this graph. In this month’s version, NSIDC also plotted the previous four years’ data (2008 through 2012). You can also see what happened to conditions during late March and early April last spring (dark green curve). A late season freeze surge occurred, which delayed the date of maximum extent by a number of weeks. Last year’s surge has no bearing on what might happen over the next couple of weeks this year. Weather conditions and some low-frequency climate oscillations (AO) are different this year and have more bearing on ice conditions than last year’s date of maximum extent.
Antarctic Pictures and Graphs
Here is a satellite representation of Antarctic sea ice conditions from February 11, 2013:
Ice growth is easily visible around the continent. There is more Antarctic sea ice today than there normally is on this date in the year. The reason for this is the extra ice in the Weddell Sea (east of the Antarctic Peninsula that juts up toward South America). This ice exists this austral summer due to an anomalous atmospheric circulation pattern: persistent high pressure west of the Weddell sea pushed sea ice north. The same winds that pushed the sea ice north also moved cold Antarctic air over the Sea, which has kept ice melt rate well below normal. A similar mechanism helped sea ice form in the Bering Sea so far this winter. Where did the anomalous winds come from? We can again point to a climatic relationship.
The difference between the noticeable and significant long-term Arctic ice loss and relative 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. This is almost exactly the opposite dynamical condition than exists over the Arctic with the negative phase of the Arctic Oscillation. The southern polar vortex has helped keep cold, stormy weather in place over Antarctica that might not otherwise would have occurred to the same extent and intensity. The vortex and associated anomalous high pressure centers kept ice and cold air over places such as the Weddell Sea this year.
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 (subs. req’d). The strong Antarctic polar vortex will likely weaken back to a more normal state and anomalous high pressure centers that keep ice flowing into the ocean will not form as often. For now, we should perhaps consider the lack of global warming signal due to lack of ozone as relatively fortunate. In the next few decades, we will have more than enough to contend with from Greenland ice sheet melt. Were we to face a melting West Antarctic Ice Sheet at the same time, we would have to allocate many more resources. Of course, in a few decades, we’re likely to face just such a situation.
Finally, here is the Antarctic sea ice extent time series through mid-March:
Given the lack of climate policy development to date, Arctic conditions will likely continue to deteriorate for the foreseeable future. The Arctic Ocean will soak up additional energy (heat) from the Sun due to lack of reflective sea ice. Additional energy in the climate system creates cascading and nonlinear effects throughout the system. For instance, excess energy pushes the Arctic Oscillation to a more negative phase, which allows anomalously cold air to pour south over Northern Hemisphere land masses while warm air moves over the Arctic during the winter. This in turn impacts weather patterns throughout the year across the mid-latitudes.
More worrisome for long-term concerns is the heat that impacts land-based ice. As glaciers and ice sheets melt, sea-level rise occurs. Beyond the increasing rate of sea-level rise due to thermal expansion (excess energy, see above), storms have more water to push onshore as they move along coastlines. We can continue to react to these developments as we’ve mostly done so far and allocate billions of dollars in relief funds because of all the human infrastructure lining our coasts. Or we can be proactive, minimize future global effects, and reduce societal costs. The choice remains ours.
Errata
Here are my State of Polar Sea Ice posts from February and January 2013. For further comparison, here is my State of Polar Sea Ice post from March 2012.
Update
I meant to include the following two graphs in this post because of the historical nature they represent.
The difference between these two graphics is obvious since they were taken near the time of minimum area (2012) and maximum area (2013). In terms of magnitude, the freeze season of 2012-2013 produced the highest amount of frozen ice area in the modern record (11.168 million sq. km.). The value of ice area last September was the lowest on record and the value of ice area earlier this month was the highest in four years. March’s area value occurred because of the factors I discussed above that boil down to this: the relative lack of thick ice in recent winters permitted rapid ice growth, albeit thin ice that melts quickly the following year. In addition to new record low area values in the future, significant oscillations from minimum to maximum and back again are likely to occur in the future as well. This does not contradict climate change; it is a manifestation of climate change. I hope write more about this topic soon, but countries are reconstructing international policy (military and economic) as a result of the changes seen in the Arctic. Those policy shifts will have societal repercussions, which I venture say few people realize today.
If you have had any exposure to this subject, you probably already have your mind made up about my title. As I’ve gained exposure, via multiple disciplines, I’ve changed my mind. And that allows me to look at climate reporting in new ways. Take this article and interview for instance. It’s meta-related, masked by the climate’s relationship to extreme weather. There are thousands of examples of conservatives ignoring science when it suits them. Doing so actually has more to do with conservatives operating from their value system. Are there similar examples of others ignoring science when it similarly suits them? I think it would be foolhardy to assume otherwise. Here is what I think about this article.
First, the mask: climate-extreme weather. There is no documented causal relationship between the two. In fact, the number of identified causal relationships between climate change and anything is still relatively small. There is a strong temperature signal. There is a growing ocean acidification signal. The sea level change signal is small but present and growing. How about precipitation? Nothing definitive. How about snowstorms? Nothing definitive.
But those signals are small against much stronger climate signals. Would something like drought or hurricanes or floods or tornadoes exhibit a stronger signal. In a word, no. There simply is not a detectable climate and extreme weather link today. That is not to say a future signal will not exist – there very well might be. But as of today, there is not. What science backs up that claim? The 2008 U.S. Climate Change Science Program’s Synthesis Report for starters (p.42; 2.2.2.1):
When averaged across the entire United States (Figure 2.6), there is no clear tendency for a trend based on the PDSI. Similarly, long-term trends (1925-2003) of hydrologic droughts based on model derived soil moisture and runoff show that droughts have, for the most part, become shorter, less frequent, and cover a smaller portion of the U. S. over the last century (Andreadis and Lettenmaier, 2006).
There is not enough evidence at present to suggest high confidence in observed trends in dryness due to lack of direct observations, some geographical inconsistencies in the trends, and some dependencies of inferred trends on the index choice. There is medium confidence that since the 1950s some regions of the world have experienced more intense and longer droughts (e.g., southern Europe, west Africa) but also opposite trends exist in other regions (e.g., central North America, northwestern Australia).
One big impediment to our extreme event trend ascertainment is our basic inability to monitor events in the first place. But based on the observations made, there is, in the IPCC’s own language, only medium confidence that droughts in some areas of the world are increasing in severity while decreasing in other places. Is climate change increasing extreme events? Not droughts – not yet.
What about storms like Sandy or Katrina (note: the former was a tropical system that changed to an extratropical system at landfall while the latter was a full-fledged hurricane at landfall)? There is at this time no global trend in hurricane frequency or intensity that demonstrates a clear causal relationship to climate change. There are indexes that a few scientists have developed to examine the data in different ways with differing results, but they require fairly complex methodologies to calculate. If I created my own index that demonstrated a relationship between the type of food I ate and climate change, does one cause the other? Certainly not directly. The hurricane-climate change relationship should exhibit a detectable signal in 50 more years or so. Until then, scientists cannot confidently say the data supports such a relationship. Extratropical storms increased in strength a little over the past century, although the locations of increase are limited. Their frequency has not increased.
Quickly, the same thing holds for floods and tornadoes. Datasets are simply too limited in space and time to currently identify a robust relationship.
As I wrote above, there are clear signals that we have already detected. The effects of those signals are mostly well-known, although some surprises are certainly in store for the planet. Extreme weather is not one of those signals. At least, not yet. If people are concerned about the level of inaction taken on climate change to date, it is folly to chase down or exaggerate signals that do not yet exist. If arguments based on signals detected are not enough to propel action, then we need to address their sets of values and how we communicate them. Fear-mongering and purposeful ignorance of science are not adequate substitutes.
Finally, I question the following from the article:
“I quote the climate skeptics or deniers — whatever term you prefer — when they’re relevant. So when I’m doing a piece about the science itself and what the latest scientific findings are, especially if that’s a short piece, I don’t necessarily feel obliged to quote the climate skeptics the same way that if you were doing a story about evolution, a New York Times reporter wouldn’t feel obliged to call up a creationist and ask them what they think. On the other hand, the climate skeptics are politically relevant at this point in American history [in a way that] the creationists are not, for example. So we have a fair chunk of the Congress … that sees political traction right now in questioning climate science or purporting not to believe it, so in a political story or in a longer story, I usually do give some amount of space to the climate skeptics.”
This quote comes from Justin Gillis, who writes about climate change for The New York Times. Does any of the above evidence make it into his interview with NPR? Here is my question: is Mr. Gillis a climate change writer or a politics writer? Scientific climate change writers should focus on the science. If Mr. Gillis wants to be a political climate change writer, he and the NYT owe it to their readers to make that distinction clear. Especially when double standards are applied to a different type of science writing. I would argue that creationists have a considerable amount of political traction right now also. I do not agree with their viewpoint, but if Mr. Gillis and the NYT want to write comparison pieces and not news pieces, I do not see why that effort should stop at climate change.
According to the Drought Monitor, drought conditions improved recently across some of the US. As of Mar. 12, 2013, 51.4% of the contiguous US is experiencing moderate or worse drought (D1-D4). That is the lowest percentage in a number of months. The percentage area experiencing extreme to exceptional drought increased from 17.7% to 16.5% in the last month. Percentage areas experiencing drought across the West stayed mostly the same while snowpack generally increased. Drought across the Southwest decreased slightly and rain from storms improved drought conditions in the Southeast.
My previous post preceded a 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, this snow represented ~1″ of water precipitation. Unfortunately, these same areas required 2-4″ of rain to break their long-term drought. In other words, while welcome, recent snows have not substantially reduced drought severity affecting the middle of the nation, as the following map shows.
Figure 1 – US Drought Monitor map of drought conditions as of the 12th of March.
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 the 12th of March.
Some small relief is evident in the past couple of weeks, 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 almost a year now.
Here are conditions for Colorado:
Figure 3 – US Drought Monitor map of drought conditions in Colorado as of the 12th of March.
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 the 12th of March.
Again, even with large snowfalls in the past month, little drought relief is evident across this region. What these states need are frequent soaking rains in the spring and summer to alleviate their long-term drought. Agriculture certainly could use that relief this year.
And finally the area that experienced the most relief in the past month, the Southeast:
Figure 5 – US Drought Monitor map of drought conditions in the Southeast as of the 12th of March.
The shifts in the numbers in the table tell a good story. Frequent storms tracked over this region recently, which helped bust the worst conditions (Severe and worse). Look at the ‘None’ category now versus three months ago: the percent area doubled! Now the rains need to continue through the rest of the year.
US drought conditions are related to 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 Nino-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, their policy responses vary. A growing number of water utilities recognize the need to be proactive 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. 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. Warmer conditions include warmer water today than what existed 30 years ago. Warmer water into a plant either mean warmer water out or a longer time spent in the plant, which reduces the amount of energy the plant can produce. 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.
According to data released by NASA and NOAA last week, January was the 6th and 9th warmest January’s (respectively) globally on record. Here are the data for NASA’s analysis; here are NOAA data and report. 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:
January’s global average temperatures were 0.61°C (1.098°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 will occur: high latitudes (especially within the Arctic Circle). The past three months have a +0.58°C temperature anomaly. And the latest 12-month period (Feb 2012 – Jan 2013) had a +0.58°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) is 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 in 2013.
Figure 1. Global mean surface temperature anomaly maps and 12-month running mean time series through January 2013 from NASA.
According to NOAA, January’s global average temperatures were 0.54°C (0.97°F) above the 20th century mean of 14.0°C (57.2°F). NOAA’s global temperature anomaly map for January (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 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 and Alaska are a concern. These areas were warmer than average during more months in recent history than not. Additionally, Australia was much warmer than usual. Indeed, Australia’s January average temperature was the highest on record: +2.28°C (4.10°F!) above the 1961–1990 average, besting the previous record set in 1932 by 0.11°C (0.20°F). In contrast to 2012, Siberian temperatures were cooler than normal. This is likely a temporary, seasonal effect. Long-term temperatures over northern Siberia continue to rise at among the fastest rate for any region on Earth.
These observations are also worrisome for the following reason: the globe came out of a moderate La Niña event in the first half of the year. During the second half of the year, 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 January 2013, in recorded history.
Skeptics have pointed out that warming has “stopped” or “slowed considerably” in recent years, which they hope will introduce confusion to the public on this topic. What is likely going on is quite different: since an energy imbalance exists (less outgoing energy than incoming energy) and the surface temperature rise has seemingly stalled, the excess energy is going somewhere. That somewhere is likely the oceans, and specifically the deep ocean. 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 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 additional water vapor. Thus, the immediate warming rate might have slowed down, but we have locked in future warming (higher future warming rate).
In a previous post on global temperatures, I pointed a few things out and asked some questions. The Conference of Parties summit produced no meaningful climate action (November 2012). Countries agreed to have something on paper by 2015 and enacted by 2020. If everything goes as planned (a huge assumption given the lack of historical progress), significant carbon reductions wouldn’t occur until later in the 2020s – too late to ensure <2°C warming by 2100. If, as is much more likely, everything doesn’t go as planned, reductions wouldn’t occur until later than the 2020s. Additional meetings are scheduled for this year, but I maintain my expectation that nothing meaningful will come from them. The international process is ill-equipped to handle all the legitimate interest groups in one fell swoop.
Instead, actions that start locally and grow with time are more likely to address emissions and eventual warming and other climate change effects. People started small-scale activities in cities around the world in recent years. There are also regional and international carbon markets. While most markets were poorly designed, lessons learned from the first generation can be used to make future generation markets more effective. As these small-scale efforts grow and their effects combine, larger bodies will need to address differences between them so that they work for larger populations and markets.
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 begins 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.
