by Shuang-Ye Wu
Dr. Shuang-Ye Wu is a climatologist working in the Department of Geology at University of Dayton. Her research focuses on how climate change alters the hydrologic cycle and the consequent precipitation patterns. In particular, she is interested in changes in extreme events such as extreme storms, floods and droughts. Dr. Wu has published 36 papers in peer-reviewed scientific journals, and obtained grants from NSF, EPA and other funding agencies. Dr. Wu obtained her Master and PhD degrees from Cambridge University in UK, majoring in environmental geography. She is currently teaching courses in the Earth system science, climate change, and geographic information systems at UD.
UPDATE 6/26/18:Steve Gollmer has posted as response to this post here (link also available in comment below).
In an Answers in Genesis article entitled “The End of Global Warming?” , Steven Gollmer – Professor of Physics at Cedarville University – cited the data of global temperature to show a “plateau” of temperature since 1998, and suggested that even “if CO2 is causing global warming, it will eventually reach a saturation point, and temperatures will level off at a new equilibrium.” Here is what is wrong with his evidence and arguments.
1. Global temperature is NOT stabilizing.
The global temperature data used by Gollmer ended at 2013. Since then, we had three consecutive record-setting years (2014, 2015 and 2016) in terms of global temperature (see figure below, data source: National Oceanic and Atmospheric Administration). Despite the bitter cold winter we experienced in the US, the year 2017 is the second warmest year on record, and the warmest year without El Niño. All but one of the 18 warmest years on record occurred in the 21st century. The only exception is the year 1998 when we had a strong El Niño. Climate system has its internal variability, so temperature can exhibit short-term increase and decrease. The so-called “plateau” is just one of those temporary variations. Despite such variability, the long-term increasing trend of the global temperature is very clear in the data, and this trend is going to continue with increasing CO2 concentration in the atmosphere because of greenhouse effect.
2. We are NOT at, or even near, equilibrium.
Gollmer used the analogy of a water bottle with holes to illustrate the idea of the equilibrium state. In order to explain this better, we need first set up the analogy more accurately. Suppose we have a water tank with an inflow and an outflow (see figure on the right). When inflow equals outflow, the water level in the tank remains constant. If we increase the inflow to a higher rate, the water level will increase. Higher water level will lead to higher pressure at the bottom of the tank, forcing the water to flow out faster. Therefore, as water level increases, the outflow will increase until it equals the inflow. At this point, the water level will reach a new stable level that is higher than before: a new equilibrium is reached for the water tank system. However, a new equilibrium (a stable water level in this case) can only be reached if the input is constant. If we keep increasing the rate of inflow, the equilibrium will not be reached until the inflow stabilizes first.
The global temperature, like the water level in the tank, changes in response to energy input and output. The Earth receives the Sun’s energy (input), and warms up as a result. As it warms, it radiates energy into the space (output). The amount of energy it radiates out depends on its temperature. Higher the temperature, more output radiation. When energy input equals output, the Earth’s temperature remains constant. If the input increases, such as more solar energy reaching the Earth or higher level of CO2 trapping more energy, the Earth will warm up. As it warms up, the Earth will also radiate more energy out. However, a stable temperature can only be reached if the change in the energy input stabilizes first. Our data shows a continued increase of the CO2 in the atmosphere (figure below) at accelerated rates. Under such circumstances, we are far from reaching an equilibrium. For a more detailed scientific explanation about why the CO2 effect is far from saturation, please see https://skepticalscience.com/saturated-co2-effect.htm.
3. A new equilibrium is NOT what we want.
It is true that the Earth will reach a new equilibrium once input stabilizes, but as Gollmer also pointed out, is the new equilibrium what we want? Equilibrium or not, it is the actual temperature increase that will affect all of us. Climate models project 2-4 degrees (Celsius) increase by 2100, 6-8 degrees increase by 2300, and 6-15 degrees of eventual increase (i.e. equilibrium) if we burn all the fossil fuel (likely within the next 100 years). To put these numbers in some context, the difference in average global temperature between Medieval Warm Period (when people settled in parts of the Greenland) and Little Ice Age (when major rivers in Europe such as the Thames froze in winter) is 0.5-0.8 degrees. Global temperature decrease during the last glacial maximum about 20,000 years ago (when large ice sheet in North America reached Dayton) is about 4 degrees. A completely ice-free Earth would be about 6-10 degrees warmer than present (Crowley and North 1991). In addition, those great climatic changes in the Earth’s past occurred over tens and hundreds of thousand years, whereas the present temperature increases occurs over just hundreds of years. The rate of change of global temperatures we are experiencing now far exceeds even the greatest rates that occurred during the catastrophic deglaciations of the Pleistocene – the most extreme and abrupt climate change recorded in the geological records. Such fast rate of change limits the ability of natural environment or even human society to adjust and adapt to the changes, leading to devastating consequences.
So no, the new state (equilibrium or not) is NOT what we want.