Climate Change: Graphs and Commentary

(ongoing essay: updated monthly, last updated May 20, 2019)

Disclaimer: I am NOT a climate scientist!


April 2019 Climate Highlights

April 2019 was horrendous although not quite so extreme as March 2019.

April 2019 was the second warmest April on record with an anomaly of 0.93° C. above the 20th Century average, roughly equivalent to 1.20° C. above pre-industrial times. The April 2019 anomaly was well below the March anomaly of 1.04° C.

Officially, the current El Niño episode began during the Sept.-Nov. 2018 three month period. A weak El Niño is predicted to continue, probably into Fall 2019. El Niño episodes tend to bring warmer temperatures.

The latest five 12 month periods ending in April are the five warmest on record. The 12 month period ending in April 2014 was the sixth warmest, insignificantly above the 12 month period ending in April 2010.

Carbon dioxide in the atmosphere continues to rise, and is now at 409.50 ppm, averaged over the latest 12 months at Mauna Loa. This is a rise of 0.25 ppm over last month.

April saw devastating floods in Mozambique, Iran and elsewhere. The April flooding does not appear to have been so widespread as in March.

“But if the watchman see the sword come, and blow not the trumpet, and the people be not warned: if the sword come and take any person from among them, he is taken away in his iniquity: but for his blood, the watchman will I hold accountable.” —Ezekiel 33:6



How to read this graph:
This graph compares each month separately to the 20th Century average (for months of that same name only) and ranks them separately. In other words: The month of March is compared only to other Marches. The month of September is compared only to other Septembers. For example: The warmest March, June and October are all colored red. The second warmest January, May and December are all colored orange. The Februaries colored light blue (2009, 2013) are both between the 11th and 15th warmest Februaries inclusive. The December colored yellow (2014) is the third warmest December and is 0.84° C. warmer than the average of all Decembers in the 20th Century. Etc.
Some points to note:
1. The data for this graph come from the National Oceanic and Atmospheric Administration (NOAA)'s climate at a glance section.

2. This graph gives the Earth's approximate average surface temperature for each month. Needless to say, distilling the world's climate into one number per month is a gross over-simplification. Further, surface temperature is only part of the story. Temperatures in the upper atmosphere and ocean depths contribute to surface anomalies through convection and heat exchange.

3. Temperature anomalies are not necessarily distributed equally around the globe. For example, while summer 2017 was third warmest globally, it was the warmest summer on record in California, which, preceded by a wet winter, contributed to devastating Summer and Fall wildfires and the mudslides which followed.

2018 brought another hot dry Summer and Fall to California with more destructive fires. While 2018 was the fourth warmest year on record, July 2018 was the hottest month ever in California.

4. Historic data may change slightly (one or two hundredths of a degree) month to month, probably due to NOAA refining its models and data-crunching techniques.

5. Every month since February 2008 has an anomaly (distance from the 20th Century average) above 0.4° C. The last month with a negative anomaly was Dec. 1984. The highest anomaly was 1.23° C. in March 2016.

6. This graph shows a short term rising trend from 2008 to the present with a bump during the 2015-2016 El Niño episode. It also shows wide variation from month to month; but the rising trend is still discernible at a glance. 2005 (not shown) was the warmest year to date before this graph. It has since been surpassed by 2010, 2014, 2015 and 2016 respectively as the warmest year to date.

7. All 12 highest ranking months lie together between Sept. 2015 and August 2016, during a monster El Niño episode. 11 of the second highest ranking months (all except Nov. 2013 which was the second warmest November), ten of the third highest ranking months, ten of the fourth highest ranking months and ten of the fifth highest ranking months all lie within the last 60 months. We have experienced a string of over five years with each month having an anomaly of 0.69° C. or greater and also being among the top ten warmest months with that same name. Four of the latest seven months were the second warmest with that same name.

8. Other models give somewhat different results. For example, the model used at Copernicus Center (ERA-Interim) rates February 2018 as the fourth warmest February. The NOAA model rates February 2018 as the ninth warmest. In the Copernicus model October 2018 is the fourth warmest October. The NOAA model rates October 2018 as the second warmest. In part, this has to do with the relative weights each model gives the arctic, which is warming at a faster rate than the temperate regions.

Which model is correct? both and neither. Models are simply simplifications of the real world. No model of a complex system is exact (otherwise it wouldn't be a model).

9. There are seven months with an anomaly greater than 1.0° C. A string of five such months (Dec. 2015 through April 2016) lie within the monster 2015-2016 El Niño (warmer) episode. During the Winter of 2018, we experienced a (cooler) La Niña episode. The February 2018 anomaly of 0.70° C. is the lowest we have seen since November 2014 which had an anomaly of 0.69° C. The La Niña episode ended in March 2018, and the world has returned to warmer El Niño conditions. Indeed March 2019 had an anomaly of 1.04° C., the highest since April 2016.

10. The last five 12-month periods ending in April (2015-2019) have been the five warmest on record. The 12-month period ending in April 2014 was the sixth warmest, insignificantly warmer than the 12-month period ending in April 2018. Eight of the ten warmest 12-month periods ending in April lie within the last ten years. (See table below.)

The five latest 12-month periods have been the five warmest since we crossed the threshold in August 2018. This situation seems likely to continue throughout 2019 and perhaps longer.
11. Temperatures appear to have risen about 0.24° C. over the last ten years (difference between average anomaly of 36 months ending April 2019 and average anomaly of 36 months ending April 2009).
Why is this graph important?
1. This is a “you can't see the forest for the trees” graph. Forests are important; but so are individual trees. Indeed, there is no forest without trees.

2. This graph allows you to see the present in detail. (present here meaning the approximate average monthly surface temperature over the latest 136 months or 11+ years.)

3. You can get a similar graph from
NOAA's Climate at a Glance section; but I like the way this graph presents the data. I think the white spaces and the color coding increase readability.

4. Why 11+ year? Why not some other period like 7 or 15 years? No particular reason. With a longer period the lines get squished together and are harder to read. Shorter periods show less data. This started out as a ten year graph but has grown longer as I add months.

5. I intend to update this graph around the 20th of each month when NOAA comes out with a new month of global climate data.

6. How did I get into this? In 2016 my favorite website for news, Common Dreams, used to report the NOAA data month after month as they set new records. They stopped when September 2016 fell to second place. Being curious, I went to the NOAA site and wondered why it wasn't reported as news that the three warmest Septembers on record were in 2015, 2016 and 2014 respectively. After a few months of silence, I decided to start reporting this data myself.

A longer term temperature graph — 30+ years


1. This 30+ year graph of 12 month overlapping periods measures the temperature anomaly from the 20th Century average. The colors refer to the El Niño / La Niña condition during the three months centered on the final month of the 12 month period.

2. El Niño / La Niña refer to cyclical changes in atmospheric and oceanic circulation patterns over the tropical Pacific Ocean. El Niño episodes usually bring warmer global surface temperatures; La Niña episodes bring cooler surface temperatures. There is a brief explanation of El Niño and La Niña here.

An ONI (Oceanic Niño Index) is computed for each overlapping period of three consecutive months based of conditions in the tropical Pacific Ocean. If the ONI index is at least 0.5 (at most -0.5) the three-month period is considered an El Niño (La Niña) period. Five or more consecutive El Niño (La Niña) periods are considered an El Niño (La Niña) episode. An El Niño episode is very strong (strong, moderate, weak) if it contains three El Niño periods with index at least 2.0 (1.5, 1.0, 0.5). A La Niña episode is strong (moderate, weak) if it contains three La Niña periods with index at most -1.5 (-1.0, -0.5). These classifications are somewhat arbitrary.

3. This graph is surprisingly smooth in spite of all the crests and troughs. The largest difference between two adjacents lines is 0.05° C.; and this occurred only twice over the period covered by the graph.

4. Exceptionally high temperature crests have followed the two very strong El Niño episodes of 1998 and 2016. Surface temperatures have fallen after the end of these El Niño episodes but remained much higher than before the El Niño episode began. This happened to a lesser extent after the moderate El Niño episode of 2009-2010.

5. We have just experienced six consecutive overlapping three-month periods with ONI indices of 0.7, 0.9, 0.8, 0.8, 0.8 and 0.8 respectively. Not surprisingly, global surface temperatures are rising again. Indeed, with an anomaly of 1.04° C., March 2019 is the seventh highest anomaly on record.

6. This graph consists of a progression of waves with increasingly high crests and troughs. Crests have increased from a height of 0.42° C. (above the 20th Century average) in 1988 to 1.02° C. in 2016. Troughs increased from a height of 0.24° C. in 1994 to 0.56° C. in 2012. (We may have hit a trough of height 0.77° C. during the summer of 2018; but it is still to early to be certain.) Temperature increases do not appear linear; they appear to be accelerating at a super-linear rate.

7. Climatewise, extrapolation and longterm prediction are a very risky endeavor. However, looking at the 30 year graph above, the latest IPCC predictions seem ridiculously conservative. I would not be surprised to see us blow through the 1.5° C. above pre-industrial levels ceiling within a decade.

8. In short: We're in terrible trouble. We better do something quick.

Another 30+ year graph — CO2 in the atmosphere


1. The data for this graph come from the average monthly readings for CO2 in the atmosphere, taken at the Mauna Loa site in Hawaii. Each line in the graph is a weighted average of the current month and the 11 consecutive previous months. (E.g.: The line for March 2018 is the weighted average of April 2017 through March 2018.)

2. CO2 (and other greenhouse gases like methane) in the atmosphere act like a one way glass allowing incoming electromagnetic radiation from the sun to pass through the atmosphere, but trapping outgoing radiation from the Earth.

3. For each month since 1987, the increase has been positive, ranging from 13 to 342 ppb (parts per billion). (I find this consistency somewhat surprising.) The average yearly increase over the period covered by this graph (since 1987) is 1.92 ppm (parts per million).

4. The increase over the past 12 months is 2.37 ppm, 23% above the average since 1987. We have a lot of work to do if we are to meet the goal of the December 2015 Paris Climate Agreement.

5. The month of February, 2019 set a new record for CO2 in the atmosphere as measured as a monthly average at Mauna Loa: 411.75 ppm. The previous monthly record of 411.24 was set in May, 2018. Significantly, the monthly record for the year is typically set in May, when northern Hemisphere trees come out of dormancy and begin to sequester CO2 in earnest. Rarely has a record month been recorded as early as February and never by anywhere near the 0.51 ppm recorded in February, 2019. February also set a record at Mauna Loa in 2017 (by 0.16 ppm), 2013 (by 0.06 ppm), and 2010 (by 0.06 ppm), all within the past decade. This could reflect an increase in CO2 produced by human activity, a failure of forests, oceans or other carbon sinks to absorb CO2, and/or other factors.

The missing graphs

Here should go historic graphs on global land use, droughts, desertification, floods, cyclones, wildfires, etc. Sadly, I have no such graphs, and not even the data to make them. Maybe later.


1. This graph (also from NOAA data) of 36 month overlapping averages (each 36 month period ending in month with same name as latest month for which data is available) from 1880 to the present shows a longer term rising trend, with an increasing rate of warming in recent years.

2. I like 36 month overlapping graphs. I think they smooth the data, but not too much. You can view 12 month or 60 month overlapping graphs at
NOAA's Climate at a Glance section too.

3. There have been various pronouncements that global warming stopped in 1998 (or some other recent year) and global cooling began. This graph demonstrates clearly, without the need for any statistical analysis, that no such thing has happened.

4. Data previous to the 1960s are from surface-based measurements and probably not as accurate as data from later years which include satellite-based measurements.

5. This graph begins about a century after the start of the “industrial revolution.” It details the sharp and increasing rise in global temperatures with the development of technology.

6. The Paris Climate Agreement seeks to limit global warming to 1.5° C. above pre-industrial times. It's uncertain what global temperatures were in the 18th Century; but 0.27° C. below the 20th Century average seems like a fair estimate. If so, we attained the 1.5° C. ceiling in March 2016, and then fell back several tenths of a degree.

I compute a 0.27° C. rise in temperature from pre-industrial times to the 20th Century average thusly: Copernicus Center computes the rise from pre-industrial times to it's base period (1981-2010) as 0.63° C. And the rise from its base period to 2018 as 0.43° C. Summing we get 1.06° C. NOAA computes the rise in temperature from its base period (20th Century) to 2018 as 0.79° C. Subtracting we get 0.27° C. Kind of like comparing apples and oranges; but it's the best I can do. If you have a better method, let me know.

Note that March 2016 is the month with the highest temperature anomaly (1.23° C.) on record according to NOAA. Copernicus's ERA-Interim model has temperatures max out at 0.86° C. in February 2016, yielding 1.49° C. above pre-industrial times, a hair below the 1.5° C. ceiling. So how many months warmer than 1.5° C. does it take to declare that temperatures have breached the 1.5° C. ceiling? IPCC is silent about this. Your guess is as good as mine.

7. What's the big deal about 1.5° C.? If (unlike yours truly) you are a normal human being, your body temperature is probably 37° C. (98.6° F.) Now raise your body temperature 1.5° C. At 38.5° C. (101.3° F.) you are probably feeling sick and better go to bed and drink plenty of fluids. Now raise your temperature another 0.5° C. At 39° C. (102.2° F.) you are feeling terrible. Suppose your temperature goes up yet another 2° C. At 41° C. (105.8° F.) you will die, if your body temperature does not come down very quickly.

The analogy is not exact. Gaia (The Living Earth) is much more resilient than we puny humans. She has weathered wilder swings in temperature than this. The climate at 4° C. above pre-industrial times would be very inhospitable to human “civilization,” with monster hurricanes, floods, droughts, and other extreme weather events which would drarf anything on Earth today. It's very unlikely that many of us would survive a 4° C. rise in the Earth's temperature.

8. Many have wondered what will happen to mankind as the climate continues to warm. Some say we will continue with business as usual; others say we will join the dodos and the dinosaurs. I suspect somewhere in between. Our current “civilization” is certainly unsustainable; but I see no reason why, with the grace of God, a few of us can't continue to live on Earth in much the same way as our ancestors did during the Pleistocene, which ended about 11,300 years ago.

“Yet will I leave a remnant, that ye may have some that shall escape the sword among the nations, ... and they shall lothe themselves for the evils which they have committed in all their abominations.” —Ezekiel 6:8-9
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Unlike the graphs above, the graphs below are based on “proxy data.” That is: global temperatures are inferred from things like tree rings, ice cores, the makeup of the shells of sea critters, type of flora and fauna in the fossil record, etc.

Needless to say the graphs below may not be all that accurate; and the further back in time we go, the less accurate they are likely to be. Nevertheless they seem to be the best we have; so let's go with them.

1. This graph is derived from research by Michael Mann published in 2008.

2. The baseline, 1961 to 1990 average, is approximately 0.12° C. higher than the Twentieth Century average used in the first three temperature graphs above. The scale is Fahrenheit instead of Celsius (1.8° F. = 1.0° C.)

1. This graph is from research by Shaun Marcott et al. published in 2013 and represents a probable reconstruction of temperatures over the last 11,300 years (Holocene).

2. During the Holocene, mankind learned to domesticate animals, build cities, develop written languages, cut down forests, burn fossil fuels, fight wars etc.

3. The baseline, 1961 to 1990 average, is the same as previous graph and is approximately 0.12° C. higher than the Twentieth Century average used in the first three temperature graphs above.

4. The gray squiggly lines at the right represent the previous graph superimposed on Marcott's findings.

5. The wide band represents probable uncertainty.

6. This graph shows global temperatures rising 0.5 to 1.0° C. until 7000 years ago and then falling back to a low close to the start of the Holocene. This low is generally called the “Little Ice Age” which lasted from 1600 to 1850 approximately. From 1850 onward temperatures have risen sharply.

7. One problem with this graph is that the right end of the x-axis (labeled 0) is “the present.” Which year is the present? This is important with temperatures rising by perhaps 0.24° C. in the last decade.

8. If we haven't already surpassed the highest Holocene temperatures, we must be getting pretty darn close.

9. It appears from this graph and the first graph presented that we have far surpassed 1.0° C. above pre-industrial times, which makes it very unlikely that we could make the Paris Climate Agreement target (no more than 2.0° C. of warming, but striving for 1.5° C.) even if we were trying hard (which we are not).

1. This graph represents a possible reconstruction of temperatures during the ice ages and the interglacial periods. (Pleistocene)

2. The scale is Fahrenheit instead of Celsius (1.8° F. = 1.0° C.) and the baseline is the average over the past millenium (possibly around 0.2° C. below the 1961 to 1990 average).

3. The Pleistocene was a succession of wide swings in temperature between ice ages and interglacials, possibly as much as 16° C.

4. Since the rise from baseline to the present doesn't appear consistent with the above graphs, this reconstruction is suspect. Since the data come from ice cores, likely they do not reflect global temperatures as a whole.

5. We are not told which year the 0 point on the x-axis represents.

6. Modern man evolved during this period, probable around 250,000 years ago. Around 50,000 years ago he began to develop more advanced technology and migrated throughout Eurasia, Africa and then Australia and even later, the Americas.

7. Since modern man has been able to survive in almost every ecosystem on the planet, it appears very likely that he will be able to survive in at least some future ecosystem.

8. The same can not be said about “civilization.” “Civilization” developed under some very specific climatic conditions that are unlikely to exist on Earth in the near future.

9. I suspect we will surpass the highest interglacial temperatures soon. (Keep in mind that the temperature has probably risen about 0.24° C. or 0.44° F. over the past decade. (See first graph above.)

1. I don't know where this graph comes from originally. It is all over the internet.

2. 65 million years ago marks the probable demise of the dinosaurs.

3. Temperatures in the Eocene, some 50 million years ago were likely 5 to 20° C. higher than today.

4. There are no known “great extinctions” during the Eocene. Indeed, life seems to have thrived during the warm period in the early Eocene.

5. Atmospheric carbon dioxide is thought to have also been much higher during the Eocene than today.

6. The Eocene might give us some clues as to what might happen on Earth in the near future.

1. I don't know where this graph comes from either. It is also all over the internet.

2. 542 million years, back to the Cambrian, is a long time. Planet Earth has weathered a lot of changes. May she also weather this one.

3. Looking at these graphs, one should realize how hard it is to predict the future. Science talks in probabilities. There are few certainties in Science.
More discussion of these and other temperature graphs to be added later

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