Responding to a climate change denier who attacks the science of Hansen et al.

I ran across this article on Steven Goddard’s blog which spews a plethora of misinformation to deny that climate change is occurring. Its level of mendacity and misdirection made me so mad, that I decided to respond in the comments section. Knowing that most comments with links are automatically rejected, I omitted including any links, but when I posted, a message appeared saying that my comment awaits “moderation”, which means that it will probably never get published, since the owner of the blog clearly has no interest in honest debate about the science. Since my comment won’t get posted, I decided to post my response here in the hope of combating the misinformation.

This is an incredibly deceptive article, written by someone who doesn’t know the first thing about climate science. I am probably wasting my time, but I will attempt to explain the problems with this article.

First of all, a lot of Hansen’s predictions are based upon paleohistory. We know that during the Eemian, which was the last interglacial 120 thousand years ago (MIS 3e), when CO2 reached a maximum of 300 parts-per-million (ppm) in the atmosphere, the temperature was roughly 1ºC warmer than today and the sea levels were 6-9 meters higher. The last time the Earth had a similar atmosphere as we have today was during the late Pliocene, 3.5 million years ago, when there was 360-400 ppm of CO2, the sea level was 22.5 meters higher than today and the temperature was 2-3ºC warmer than today.

So we know from paleohistory that our atmosphere today of 400 ppm of CO2 will produce much higher temperatures and much higher sea levels in the long term. The debate is how long will it take before we come into energy balance and the temperatures will stop rising. Currently the oceans are absorbing 93% of the total heat, whereas the atmosphere only absorbs 2%, so we still haven’t experienced the majority of the heating, which will come in the future. It takes a long time to heat up the ocean which is an average depth of 4 km deep. Likewise, it takes a long time to melt the Greenland and Antarctic Ice sheets, so there is a lag between the changes in the level of greenhouse gases in the atmosphere and the changes in the temperature and the sea level. Eventually, however, the ocean will stop absorbing heat and the heat it has absorbed will start being emitted into the atmosphere, which will warm the surface temperature. Likewise, as the icesheets melt, there will be less ice on the planet to absorb heat. Currently the Earth is absorbing more energy than it is emitting, but eventually this energy imbalance will end and we will see the same temperature and sea rises that occurred in the past when there were high levels of greenhouse gases.

The big debate among the scientists is how fast will the changes occur, not whether they will eventually occur. James Hansen and a growing number of his colleagues believe that the change will occur much faster at an exponential rate, but the consensus view as expressed by the IPCC is that these changes will occur much slower at a linear rate. There is a growing body of evidence from the paleohistory that sea level and temperature changes reach tipping points and then changes quickly accelerate. Hansen and his coauthors have looked at that evidence and predict that the same will happen today. After having read a half dozen of the recent articles by Hansen et al., I find their arguments very convincing why we can expect rapid climate change in the future. Based on the paleoclimate, they argue that we need to reduce the CO2 levels to 350 ppm, or possible to 300 ppm if we want to stabilize the climate.

Now this article criticizes Hansen because he predicted back in the late 1980s, that we will start to see rapid temperature and sea rise within 20 or 30 years time. Predicting when tipping points will be reached and strong feedback loops will kick in is extremely difficult, especially in 1988 when there is was limited historical data from the ice cores and ocean floor samples. Today we have much better paleoclimate data, and most climatologists agree that abrupt climate change will probably happen if we continue on the current trajectory. They just don’t agree when it could happen.

If we stabilize the level of greenhouse gases in the atmosphere at today’s levels, most scientists predict that the sea will be roughly 25 meters higher than today in the year 4000, because they can see those sea levels in the paleohistorical record, but is very hard to predict how soon the seas will rise, because we don’t have good models for how ice sheets melt, nor do the models incorporate the topography of Greenland and Antarctica, which determines how fast the sheets can slide into the sea. Likewise, it is very hard to predict how fast temperatures will rise, because we have to be able to model heat flow in the oceans, cloud formation, and dozens of other factors which are not well understood.

Most models used by the IPCC Assessment Reports have left out important feedback loops, so they predict linear change, but the paleohistorical record shows that climate change doesn’t occur linearly. Most feedbacks aren’t well enough understood to accurately model them. For example, we now know that roughly 25% of the warming which has occurred was caused by the disappearance of 40% of the area of the Antarctic sea ice which changed the Earth’s albedo (reflectivity), but most models still don’t incorporate the positive feedback from melting ice. Nobody is sure how to model the way that rising acidity in the ocean and rising temperatures are reducing the phytoplankton which is the biggest carbon sink on the planet. There has been some modeling of tropical forest dieback, which is the second largest carbon sink on the planet, but again, the CMIP5 models used in the IPCC’s Fifth Assessment Report don’t include that positive feedback.

The real disagreement among climate scientists is whether we should take drastic action now as Hansen argues because abrupt climate change is possible by mid-century or whether we can reduce greenhouse gas emissions gradually, because the radiative forcing has to be much higher to cause abrupt climate change.

This article argues that we can’t trust NASA scientists because they have mispredicted highly stochastic events like annual ice melt and el Niño. Yes, professional scientists do get this stuff wrong occasionally, but this article cherry picks a few mispredictions. For example, I could just as easily point to the time that Hansen et al. accurately predicted the change in radiative forcing and resulting temperature that would occur from the SO2 that was released by the eruption of Mount Pinatubo in 1991. Short term weather prediction is highly variable, but long-term climate trends are less variable, and prediction is more reliable.

Most of the “evidence” presented in this article is cherry-picked and doesn’t present the whole picture. The high temperatures in the US during the 1930s were an anomaly compared to the rest of the world, so you can’t just look at the US temperature trends to understand climate change which is a global phenomenon, and you certainly can’t use the raw temperature data, which distorts change over time. The Arctic sea ice has lost 70% of its volume since the late 1970s. Both Greenland and Antarctica are loosing ice volume at accelerating rates. The growth of sea ice around Antarctica is actually a result of climate change, but looking at Antarctica as a whole shows that it is loosing ice. Likewise, just looking at one season’s ice growth in the Arctic and ignoring the trend over 40 years is not honest science.

The argument in this article that NASA GISS is fraudulently manipulating the temperature record is frankly baloney. In order to get an accurate measurement of temperature change over, the raw temperature data has to be adjusted. NASA, NOAA, the Hadley Center, and every other reputable climatological organization adjusts their raw temperature data.

Here is what the NASA GISS FAQ has to say about the adjustment of raw temperature data:

Q. Why can’t we use just raw data?
A. Just averaging the raw data would give results that are highly dependent on the particular locations (latitude and elevation) and reporting periods of the actual weather stations; such results would mostly reflect those accidental circumstances rather than yield meaningful information about our climate.

Q. Can you illustrate the above with a simple example?
A. Assume, e.g., that a station at the bottom of a mountain sent in reports continuously starting in 1880 and assume that a station was built near the top of that mountain and started reporting in 1900. Since those new temperatures are much lower than the temperatures from the station in the valley, averaging the two temperature series would create a substantial temperature drop starting in 1900.

Q. How can we combine the data of the two stations above in a meaningful way?
A. What may be done before combining those data is to increase the new data or lower the old ones until the two series seem consistent. How much we have to adjust these data may be estimated by comparing the time period with reports from both stations: After the offset, the averages over the common period should be equal. (This is the basis for the GISS method). As new data become available, the offset determined using that method may change. This explains why additional recent data can impact also much earlier data in any regional or global time series.

Another approach is to replace both series by their anomalies with respect to a fixed base period. This is the method used by the University of East Anglia’s Climatic Research Unit (CRU) in the UK. The disadvantage is that stations that did not report during that whole base period cannot be used.

More mathematically complex methods are used by NOAA National Centers for Environmental Information (NOAA/NCEI) and the Berkeley Earth Project, but the resulting differences are small.

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