The extremely high level of confidence from the scientific community regarding Anthropogenic Climate Change is not based on hearsay or “just” climate models; there are completely explainable smoking guns.
Ghosh and Brand (2003) explain exactly how we know for a fact that humans are responsible for the excess CO2, and how that CO2 is what is absorbing the vast majority of the excess heat. In a nutshell, there is (or was to be more precise) basically a constant ratio of Carbon-14 to Carbon-12 because of cosmic rays interacting with the atmosphere and creating a certain amount of C-14. Fossil-fuel burning produces almost exclusively Carbon-12 because the C-14 in oil and coal has long decayed because of its age. Spectrometers can be aimed at the sky to measure exactly what elements in the atmosphere are holding the excess heat, and lo and behold, it’s C-12. The article can answer any other questions on C-14 and C-12, how we measure it, how we know where it comes from, etc. You can read an article from Skeptoid summing it up (Dunning, 2016).
And despite new attempts by obscurantists to incite doubt of CO2’s historic capacity as a greenhouse gas, we can look at the studies themselves and confirm CO2’s potency as a greenhouse gas in the past. A study by Royer, Berner, & Montañez (2004) links CO2 directly as the driver of Phanerozoic temperature increase; so does another by Frakes, Francis & Styktus (2005); and another by Berner & Kothavala (2001); and yet another by Fielding, Frank & Isbell (2008). These studies also demonstrate that after this CO2-caused warming, the Earth didn’t cool into the next ice age until CO2 was weathered out of the atmosphere and turned into limestone and absorbed in forests which were buried to form coal. Then, temperature finally drastically rose once more when two flood basalt events pumped colossal amounts of CO2 into the atmosphere again; one from the the Siberian Traps (Reichow et al., 2009), the other from the Central Atlantic magmatic province (Marzoli, Bertrand & Knight et al., 2004). Later, the next big cooling trend coincided with a drop in CO2 from it being weathered out of the atmosphere again and deposited as calcium carbonate in limestone (Maher & Chamberlain, 2014).
You can debate on how to address Climate Change given the facts, but you can’t just change reality to fit your ideology because the evidence is inconvenient.
But what about the Vostok ice core? Didn’t that prove temperature increase always precedes CO2 increase?
To begin with, the Vostok ice core (first analyzed in 1999) doesn’t say much about global climate one way or the other; it indicates historic Antarctic climate, not global climate.
The claim that it proves temperature change usually precedes CO2 increase originates from a Caillon and colleagues (2003) study where climate “skeptics” fixate on the part where researchers say there was an ~800 year lag of CO2 behind temperature in the Antarctic during a single time period called Termination 3. What the climate change “skeptics” leave out is that Caillon and colleagues concluded that temperature lagged behind CO2 in the northern hemisphere and throughout as a global average in the same time period. A paper by Shakun and colleagues (2013) replicated this finding.
The evidence says literally the opposite of what deniers of AGW claimed, and they don’t seem to understand that CO2-based greenhouse effects can occur even if a change in CO2 wasn’t the initial trigger. In fact, that is precisely what Caillon and Shakun (2003; 2013) concluded as the reason for the Antarctic warming; the Earth’s Milankovitch cycle causes a little initial warming in Antarctica, this melts ice and causes the release of trapped CO2, that CO2 floods the rest of the globe and causes global global warming. This isn’t that hard to understand.
So this climate denial argument is based on scientific papers that say the opposite of what the deniers are implying they say, and the lack of understanding that identifying other things that trigger warming (like Milankovitch cycles) does not prove that CO2 doesn’t also cause warming. For example, if you say a flu can kill people, that wouldn’t prove that a knife can’t also kill people.
CO2 and Temperature don’t correlate?
Sometimes people use a certain picture to say there is no correlation at all between temperature and CO2 historically. There is problem with the graph though. The graph comes from a blog and not a peer-reviewed academic journal.
But the real problem is that the graphic is ignoring (intentionally) that scientists know why carbon and temperature aren’t more perfectly aligned; solar output. Studies by Royer (2006) and Shaviv and Veizer (2004) have long adjusted for solar output and found CO2 and temperature to be highly correlated (the picture below). So the above picture is just another example at denialists grasping and straws, assuming that because they’re too dense to understand something everyone else must be too.
Is it the Sun controlling temperatures?
This is a pretty easy claim to debunk. For the last 40 years Sun irradiance has been decreasing while temperature has continued to increase at an alarming rate (Lockwood, 2015; Yeo et al., 2017).
In a spin-off of this bit of bunk, a Breitbart article titled “‘Winter Is Coming’ Warns The Solar Physicist The Alarmists Tried To Silence.” Astronomer Phil Plait debunked this when he pointed out that Valentina Zharkova (the author of the article cited by Breitbart) was “not predicting a 60 percent drop in the light and heat emitted by the Sun, but a drop in magnetic activity in the Sun. This has only a marginal effect on the Sun’s light/heat output.” Moreover, looking at historical temperature from Marcott and colleagues (2013), the “little ice age” that Breitbart mentioned was not actually that much colder than the surrounding centuries/decades (about a 0.18 degree Celsius drop in surface temperature from ~1500 to ~1800, compared to a roughly 1.0 degree Celsius increase in temp from ~1800 to ~2000). A one degree change in Celsius is equivalent to a 1.8 degree change in Fahrenheit for those who aren’t familiar with the Celsius scale. Clearly the Maunder Minimum was drastically less potent than the industrial revolution.
Many armchair scientists have claimed that the Earth has not warmed in 15-20 years; this is false.
Satellite temperature is often the go-to for those who don’t accept AGW because they believe it supports their argument. In most cases, what they use to prove their point is an old graph from a UAH report by John Christy and Roy Spencer that seemingly showed next to no warming (Christy, Spencer, & Braswell, 2000). However, in each revision of their report, they repeatedly identified mistakes they had to fix. At one point, satellite temperature researchers from RSS pointed out to UAH that they made yet another mistake by not adjusting for diurnal shift (Mears & Wentz, 2005), prompting the lead author of UAH’s study, John Christy, to acknowledge the mistake, correct for it, and resulted in their data now showing a steady and consistent warming trend (Wigley et al., 2006). Climate change deniers, however, still dishonestly continue to use the old graph to push a false narrative because intellectual honesty apparently isn’t a value they posses.
This brings up another point. Deniers often introduce this debunked claim by saying “let’s look at the satellite data, it is the most accurate data.” Of course they don’t say it is the most accurate data because it is, they simply define whatever data they think helps their case as automatically the most accurate. Satellite data is actually notoriously unreliable, as the example of UAH’s repeated miscalculations prove. Satellite sensors don’t directly measure temperature, they measure radiance. To infer temperature, the raw radiance data collected by the satellites must then be analyzed by complex algorithms that are only as good as the analysts who implement them. UAH and RSS are looking at the same data from the same satellites and are only doing the number crunching themselves.
Another common technique climate change “skeptics” use to deny the warming is to claim that there has been no warming since 1998. The year 1998 isn’t chosen by accident; it was part of an abnormally high spike in temperature (largely driven by an abnormally powerful El Niño). This single data-point is then compared to another single data-point cherry picked for a low temperature (2013 for example), they throw out all the data between, and voilà, they now think they’ve disproved the warming trend when they’ve done no such thing. Two data-points are not a pattern, you need all the data to be able to apply that word. Current satellite temperature data is as follows:
Remote Sensing Systems or RSS (above picture) measured that from 1979 to 2017 lower troposphere temperature has risen at an average rate of about 0.18 degrees Kelvin per decade (0.32 degrees F per decade).
The University of Alabama in Huntsville (Christy & Spencer, 2019)—the same UAH whose old report skeptics misuse—today reports that from Nov. 16, 1978 to 2019 the lower troposphere has averaged a 0.13 C increase per decade, putting us up 0.29 degrees Celsius (or about 0.52 degrees Fahrenheit) above 30-year average. Globally, the warmest years from 1979 (where the satellite data begins) to 2017 are as follows: 2016 (+0.513 C), 1998 (+0.484 C), 2017 (+0.375 C), 2010 (+0.336 C).
Comprehensive Temperature Data, Independently Collected
Of course, satellite surface temperature data is far from being the only surface air temperature data (there is weather balloon data and weather station data just to name a few).
Additionally, it is truly telling that opponents choose to focus on satellite lower troposphere data only, at the exclusion of all other data. This is an awfully convenient omission considering the scientific data specifically points out that 93% of all the excess heat is taken up in the ocean. Surface air temperature is only half the story (less than half actually). NASA, NOAA, the JMA, and the UK Met Office reports include ocean temperature data as well as surface air temperature, giving a much fuller and less erratic picture of global temperature.
The Japan Meteorological Agency showed that from 1891-2018, average global surface temperature rose 0.73°C per century since 1891, with the hottest years being 2016 at (+0.45°C) above the 1981-2010 average, 2015(+0.42°C), 2017(+0.38°C), 2014(+0.27°C), 1998(+0.22°C), and 2013/2010(+0.20°C).The UK Meteorological Office, using HadCRUT4 data, found the Earth 1.1 degrees Celsius from 1850 to 2018. The Goddard Institute for Space Studies (GISS) at NASA uses their GISTEMP data-set to measure temperature trends. They have recorded that average global temperatures have increased by 1.05 degrees Celsius since 1880.
The National Oceanic and Atmospheric Administration (NOAA), using their MLOST record, has measured that has measured a 1.01 degrees Celsius increase in global temperatures from 1880-2017, with 2016 being the hottest year, followed by 2015, 2017, 2014, and 2010.
If you wanted to say they were lying about the numbers, you would be implying that there has been a century-long conspiracy that every organization from multiple countries around the world, made up of hundreds of thousands of workers, have been conspiring together in perfect coordination and without any slip-ups to lie to everyone. And for what? To help American liberals raise taxes?
But what about the historical temperatures? Wasn’t the Medieval Warm Period hotter than today?
Let’s take a look even further back than 1850. Rohde et al. (2013), found that from 1753 to 2011 average land temperature increased by about 2 degrees Celsius.
In the process, this team also factored in the sun and found that it is not the driver of the temperature increase. Also notable in their data is that the last 50 years have been much hotter than at any point since 1753.
Michael E. Mann released a reconstruction of temperature for the years 1400–1980. The graph in the paper became known as the “hockey stick.” Denialist quickly began throwing accusations about Mann supposedly committing methodological errors and such. Climate “skeptics” attempted to use the Little Ice Age and Medieval Warming Period to disprove Mann’s results. They were apparently oblivious to the fact that the Little Ice Age and Medieval Warming period were regional phenomena and not global.
Moreover, repeated subsequent studies such as that by Wahl and Ammann (2007) re-verified over and over again Mann’s results, doing this while accounting for the “errors” deniers claimed in Mann’s original paper. Mann has now been completely vindicated but partisan enemies of science continue to claim that Mann’s results have been “debunked” because they have ignored the later studies.
Going back a full 11,300 years, Marcott, Shakun, Clark, and Mix (2013) discovered that the earth is drastically hotter now than at any point in that time period, and that the speed of increase was monumentally faster than at any point within the last 11,300 years. One very important point to make about Mann and Marcott’s long time scale temperature studies is that we can see that climate always changes, but what climate never does is change anywhere even beginning to approach as quickly as we have recently observed—at least not without some catastrophic event like an asteroid impact or a super-volcano eruption.
The canard that the denialists use about climate “always changing” needs to stop, because it’s not just that it is changing, it’s that the climate is changing at a rate completely unprecedented in Earth’s history other than during massive extinction-causing asteroid impacts and atmosphere-choking supervolcano eruptions.
Haven’t the scientific models, especially from the IPCC, been wrong? Didn’t they fear-monger and overestimate warming? No.
Climate scientist James Hanson in 1988 gave 3 scenarios called a, b, and c that estimated future surface air temperature (Hansen et al., 1988). Both a and b were somewhat higher than what happened, but actual temperatures were well above c, and still closest to b. That is not “way off,” or very far off at all, and certainly is not “alarmism.”
The IPCC prediction was even better than Hanson’s (Houghton, Jenkins, & Ephraums, 1990). On page “XIX” or (27 in the PDF) of the first IPCC report from 1990 their scenarios B, C, and D all assume about 400ppm of CO2 by 2020, negligibly off from the 410ppm as of 2018. Moreover, on page 31 of that same report, scenarios B, C, and D all predict ~1.6 degrees above 1765 by about 2018; as of 2018 we were 2 degrees Celsius above 1765. On page 30, we see that they compare their three models: High estimate, best estimate, and low estimate.
Our current 2 degrees puts us above their best estimate of 1.7 degrees above 1765, though well below their high estimate 2.5 degrees. Their low estimate was roughly 1.2 degrees.
The earlier mentioned RSS satellite temperature visual also included a representation of NASA’s CMIP-5 climate simulations, showing again that actual temperature measurements were almost entirely in-between the best and worst case estimates. It also tended lower on the prediction, but was overall still in line with predictions. In a 2013 article citing scientist Roy Spencer, it was clear he jumped the gun by declaring that the predictions have failed, and their “day of reckoning” had come (Watts, 2013). Well, as the RSS data shows (and currently Spencer’s own UAH data also shows), temperature drastically shot up 2015-17, bringing averages well within predictions. The 2013 article proved to be a little premature. Looks like the “day of reckoning” was later than Roy Spencer thought, and was against him rather that with him. It is worth emphasizing here that Roy Spencer is part of the science team at University of Alabama Huntsville that on at least 8 occasions between 1992 and 2005 had to correct serious errors in their temperature calculations which had erroneously calculated much lower than actual temperatures. He and his team have been far from the most reliable climate scientists.
So when climate “skeptics” trot out the hackneyed old “well the predictions were wrong” talking point, they are either completely clueless of the actual data, or are blatantly lying. Don’t claim the scientists were wrong when what you really mean to say is that some people who took the worst case scenarios of scientists (like Hanson’s Scenario “A”) and treated them as the most probable were wrong .
Carbon dioxide-driven anthropogenic climate change has been extensively and vigorously studied, and nearly every ounce of evidence supports it as a fact. It is not a conspiracy by liberals or China, and the evidence is accessible to the general public if they should seek it. Climate scientists have already adjusted for every factor denialists bring up, such as solar output, Milankovitch cycle, and all the other known natural cycles and factors. It is curious that laypeople so often believe themselves to be aware of more such natural cycles and factors than the professionals in the field. The verdict is in, and it has been in for a while.
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