I read the paper. This is why NO ONE understands what the fuck Climate Scientists are saying.
Really, WTF are they saying here:
A fundamental problem here, however, is that correlation between different variables does not necessarily imply causation. As stated by Barnard: “That correlation is not causation is perhaps the first thing that must be said.” Therefore the actual high correlation between rising CO2 levels and increasing surface temperatures alone is insufficient to prove that the increased radiative forcing resulting from the increasing GHG atmospheric concentrations is indeed causing the warming of the earth.
(Barnard is a ASS. One of the foundational case studies of modern epidemiology is based on the “waterpump handle” in London. Guess what! Sometimes correlation IS causation. In epidemiology that’s what you look for first.
Citing him is a classic Climate Moderate tactic, defending mistaken assumptions about the Climate System in a cloud of FUD).
Another problem contributing to the remaining uncertainty is the unclear feedback mechanism between global temperature variability and GHG dynamics that could contribute to amplify the global warming rate. A first study based on statistical methods for testing causality of human influence on climate applied Granger causality.
They found bi-directional causality between Northern and Southern Hemisphere temperatures, a result that is however not conclusive as these temperatures are not independent from each other and are both driven by the global forcing.
Interpretation: It sure looks like warming caused by CO2 but we cannot say it's 100% "beyond a shadow of a doubt certain".
Further work based on an improved methodology however confirmed that anthropogenic forcings seem to “Granger cause” temperature changes. In this study, we use a recently developed mathematical method which is capable of quantitatively evaluating the drive and feedback causal relation between time series, to address the importance of the different forcing components on climate in a quantitative but model independent way.
Interpretation: Some asshole cited Barnard like he was an oracle of absolute certainty and raised a question about causality and correlation. So we had to waste years of effort "proving" him wrong. DELAY is the name of the game for people who bring up Barnard.
This new method is based on the information flow (IF) concept. The whole new formalism is derived from first principles, rather than as an empirically defined ansatz, with the property of causality guaranteed in proven theorems. This is in contrast to other causality analyses, say that based on Granger causality or convergent cross mapping (CCM)35.
The resulting formula is concise in form, involving only the common statistics, namely sample covariances. It also allows an explicit discrimination between correlation and causality: causation implies correlation, but not vice versa.
Conclusion: CO2 is causing warming.
Also this paper is 7 years old. It’s dated.
