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IPCC Second Assessment -- What we can learn from a 30 year old report (WG1)

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The Intergovernmental Panel on Climate Change (IPCC) was established in 1988. It produced its Second Assessment Report in 1995. 3 decades later, it's worth asking, how far have we come since then? - - - Other posts in this series: First Assessment Report: WGI | WGII | WGIII - - - Working Group I (The Science) One need only look at the structure of the Summary to get a broad snapshot of what was known then. Greenhouse gas concentrations had continued to increase since the previous report, aerosols were known to lead to cooling in some areas, the climate was known to be changing and there was reason to believe it was changing due to human activities. (This is an interesting nuance -- detecting a change is not the same as attributing it to human activities -- Gavin Schmidt elaborates on this here .) The climate was expected to continue to change and many uncertainties still remained. It was known quite clearly that -- " Many greenhouse gases remain in the atmosphere for a long ...
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What is ENSO? Page 2 - SSTs and trade winds

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  This is Page 2 of the sub-series "What is ENSO?". If you haven't already, please read Page 1 first. For convenience, keep that page open in a different tab. = = = What is ENSO? In the previous post , we learnt to identify ENSO phases from the perspective of sea surface temperature anomalies . In this post, I'm going to answer a question that no one really asked ―  What if I wanted to identify ENSO phases from the perspective of sea surface temperatures (SSTs) instead? What if, for no good reason but because I felt like it, I wanted to do away with the "anomalies" bit? Looking at SSTs instead of SST anomalies makes matters unnecessarily complicated, but we're going to do it anyway because it also teaches us a lot. In the image below, I've plotted SSTs from the HadISST dataset. These are mean SSTs for the months of December, January and February (DJF) over all years from 1872-2009. Why did we select the months of DJF? Because ENSO events can be seen...
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Simply put: Hausfather et al. (2019)

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This post is based on the paper " Evaluating the Performance of Past Climate Model Projections " by Hausfather et al. (2019) published in Geophysical Research Letters. It explores an important question: How well did early climate models capture climate change?   Image source   Note that this study focused on a previous generation of climate models. Today, these models are operationally obsolete, i.e. they are no longer used for climate projections as they have been superseded by improved and more advanced models. But results from these modelling studies provide outputs for long timeframes. For examples, the oldest studies considered (Manabe, 1970; Mitchell, 1970 and Benson, 1970) provide data for 30 years from 1970 to 2000. In contrast, at the time this paper was being written, the newest study included (from the IPCC Assessment Report 4) provided only 10 years of data from 2007 to 2017. So even if this study does not tell us, How well do current climate models capture climat...
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