New Study Narrows the Range Planet’s Future Temperature

NOAA graph. Data from NOAA and ETHZ. Our World in Data and the Global Carbon Project. 

For four decades scientists, government policy makers, the IPCC and activists have used the same warning: if the preindustrial concentration of CO2 in the atmosphere doubles from the 280 ppm to 560 ppm the planet will warm between 2.7-8.1 degrees Fahrenheit (In degrees Celsius the range is 1.5-4.5.) That is a big range for global warming- from adaptable to catastrophic.

Now, a new research paper conducted under the World Climate Reasearch Programme (WCRP) and funded in part by The Department of Energy Office of Science, Office of Biological and Environmental Research, was published two weeks ago in Reviews of Geophysics. Because of the public funding, Lawrence Livermore Laboratory makes the article available for free at this link.

The research was made possible by bringing together an international team of researchers from a wide range of climate disciplines. Using temperature records since the industrial revolution, paleoclimate records to estimate prehistoric temperatures, satellite observations and detailed models that examine the physics of interactions within the climate system, the team was able to narrow the likely temperature range to 4.7-7.0˚F. (This is equivalent to between a warming range of between 2.6°C and 3.9°C.)

Since 1800 when temperature records began, average surface temperatures have risen by almost 2 degrees Fahrenheit or 1.1 degrees Celsius. The planet has not been warming uniformly. The Pacific and Southern Oceans have acted as a heat sink for those portions of the planet. Eventually, those waters will warm and increase cloud cover above the oceans. Global CO2 emissions have continued to grow and scientists are forecasting that atmospheric CO2 concentrations will reach 560 ppm by 2060. Science Magazine published an excellent review and summary by Paul Voosen at this link.

The amount of carbon dioxide in the atmosphere is still the key element that mankind can change. CO2 in the atmosphere (pink line in chart at top) has increased along with human emissions (blue line) since the start of the Industrial Revolution in 1750. Emissions rose slowly to about 5 billion tons a year in the mid-20th century before skyrocketing to more than 35 billion tons per year by the end of the century.

Based on air bubbles trapped in mile-thick ice cores (and other paleoclimate evidence), scientists know that during the ice age cycles of the past million years or so, carbon dioxide never exceeded 300 ppm. Before the Industrial Revolution started in the mid-1700s, the global average amount of carbon dioxide was about 280 ppm.

By the time continuous observations began at Mauna Loa Volcanic Observatory in 1958, global atmospheric carbon dioxide was already 315 ppm. On May 9, 2013, the daily average carbon dioxide measured at Mauna Loa surpassed 400 ppm for the first time on record. Scientists once hoped that CO2 emissions could be held below the “tipping point,” now the plan is to quickly reach peak emissions and then reverse course reducing global net human-caused CO2 emissions by about 45 % from 2010 levels by 2030 and reaching ‘net zero’ emissions around 2050. (Forbes, 2019). The current strategy  requires that fossil fuels are replaced by low or no-carbon technologies and we further decouple global GDP from CO2 emissions.