A new study finds that a doubling in atmospheric CO 2 concentration is more likely than not to cause a doubling or tripling of global temperatures, and it comes with a warning that the effects of a doubling might not be quite as pronounced as first thought.
The researchers used data from around the world, and the most detailed data available to date, and concluded that if we want to avoid dangerous climate change, we need to increase the amount of carbon dioxide in the atmosphere to at least 450 parts per million.
It’s also a more accurate guess than the previous estimates by scientists.
But the paper does highlight a caveat: the researchers don’t know how much we can expect to see in the next century.
“A doubling of CO2 concentrations, like a doubling globally, is likely not to be significant,” the authors write.
“In the past, a doubling has been attributed to an increase in global average temperature, and a doubling may also be attributed to a decrease in global mean surface temperature.
However, if the warming trend continues as predicted, then the doubling may be negligible.”
The study comes on the heels of a series of papers on the topic, with many of the authors saying that a double-digit rise in atmospheric concentrations is “not possible”, and a lot of uncertainty remains.
For example, it’s not clear if we’ll see a warming of 2C or 1.5C in the world by 2100, and some scientists believe that the warming will be much lower than that.
The uncertainty around that estimate is particularly large because the research focuses on a doubling, rather than a doubling and tripling.
It also means that it’s difficult to say how much warming we’re likely to see as a result of a doubled-up concentration.
The paper from the University of Cambridge, which also included data from a number of other researchers, was one of the first to come to this conclusion.
Its authors looked at all of the world’s carbon dioxide measurements from the 1970s and 1980s, which showed a doubling that was not expected, and compared that to current trends.
That work found that a one-cent-per-ton increase in CO 2 would cause a temperature increase of 0.25C in an area of land the size of the United States.
That would be “significantly less than the predicted warming of 0,8C in 2100, as predicted by IPCC models”, the authors wrote.
But they also said that the amount that was expected would vary greatly depending on the size and shape of the area affected.
“Even if we assume that doubling is less likely than expected, we still find a large uncertainty about the range of values for the temperature increase and the likelihood that the doubling is likely,” they wrote.
The team looked at the “total atmospheric concentration” (TCC), which is the total amount of CO 2 in the Earth’s atmosphere, and “temperature” (TPC), the amount at which it varies.
The latter is defined as the temperature difference between the atmosphere and the ground, where it would most likely affect the amount we experience in the form of precipitation.
The authors also looked at what happened in other parts of the Earth, and how it affects temperature and precipitation.
But their findings are somewhat less clear-cut than what was previously reported.
“It is possible that TCC and TPC may differ substantially from one place to another,” the researchers wrote.
They found that TMC is the “main determinant of the average temperature of the land surface” and that “the temperature difference across the surface of the earth is related to the total temperature difference” and not just TCC.
“Therefore, the observed temperature of tropical regions of the globe may vary significantly from that of the tropical regions in the north of the tropics,” the paper concluded.
“This variability may also contribute to the observed variability of the rainfall in tropical regions,” they added.
That could be due to a difference in cloud cover, which can make the difference between getting rain and not getting rain.
And that variability is not something that we’re used to seeing from humans, and is something that scientists aren’t entirely sure about.
In the paper, the authors looked through temperature measurements from satellites, which has led some to suggest that we are experiencing a cooling of the climate.
But that’s not the case.
The satellite data showed that temperatures did not change much from 1970 to 2015, which means the “warming of the planet” is actually the cooling of global surface temperatures.
“Global temperature trends are generally robust to the measurement of atmospheric temperature, as the measured temperature is typically used as a proxy for global surface temperature and is a reliable proxy for the global temperature change over the past few decades,” the study said.
But what about the effects that a global temperature rise of two degrees Celsius (three degrees Fahrenheit) is going to have on precipitation?
“The effect of doubling of global CO2 concentration on precipitation in the United Kingdom and the United Arab Emirates is likely negligible