A new climate temperature timeline

Lots of sources are reporting that climate and computer scientists have produced a timeline for Earth’s surface temperature over the last 485 million years. It is the most accurate data generated to date. It relies on a combination of the best climate models currently available and a data analysis protocol called data assimilation, something weather forecasters use all the time. A science source comments:

A reconstruction of GMST (global mean surface temperature) spanning most of the Phanerozoic Eon), PhanDA, provides a statistically robust estimate of GMST through the Phanerozoic. We find that Earth’s temperature has varied more dynamically than previously thought and that greenhouse climates were very warm. CO2 is the dominant driver of Phanerozoic climate, emphasizing the importance of this greenhouse gas in shaping Earth history. The consistency of apparent Earth system sensitivity (∼8°C) is surprising and deserves further investigation. More broadly, PhanDA provides critical context for the evolution of life on Earth, as well as present and future climate changes.  

In other words, (i) the Earth's average surface temperature has varied a lot more than we previously knew, and (ii) this is more evidence of the role of CO₂ in driving climate change. That assumes the data is accurate, something that is open to question and hard to test without a lot more research effort, assuming the data is reasonably testable. The WaPo reports (not paywalled): 

Highest average surface temperature: 96.8ᵒ F

“We know that these catastrophic events … shift the landscape of what life looks like,” [Emily Judd, a researcher at University of Arizona and the Smithsonian specializing in ancient climates and the lead author of the study] said. “When the environment warms that fast, animals and plants can’t keep pace with it.”

Rate of increase due to humans is 

the fastest known so far

Plants and animals cannot keep up,

so tens of thousands of species will go extinct

This is one of the more sobering revelations of the research, Judd said. Life on Earth has endured climates far hotter than the one people are now creating through planet-warming emissions. But humans evolved during the coldest epoch of the Phanerozoic, when global average temperatures were as low as 51.8 F (11 C).

Without rapid action to curb greenhouse gas emissions, scientists say, global temperatures could reach nearly 62.6 F (17 C) by the end of the century — a level not seen in the timeline since the Miocene epoch, more than 5 million years ago.

Humans have caused the fastest 

known rate of temperature increase

As usual, this data and analysis will be refined, critiqued and debated. But if it is reasonably close to past reality, this is another useful data point about the effects humans are having that cause climate change. About 150,000 data points were included in the modeling here. About 1.5 million would be needed to provide more confidence in the analyzed data. That will probably happen in coming years

By Germaine: Deeply skeptical of climate science skeptics