From the abstract of Gavin Schmidt’s latest
Climate models projected stronger warming over the past 15 years than has been seen in observations. Conspiring factors of errors in volcanic and solar inputs, representations of aerosols, and El Niño evolution, may explain most of the discrepancy.
Hubert Lamb offered this thirty years ago
it is clear beyond any doubt that there are other influences which also change climate and which were deeply involved in the last glaciation in particular. (The Earth’s orbital changes and volcanic dust can both be specified in this case). So, one must be suspicious of attempts to explain all the major turns of the Earth’s temperature history in terms of just one variable such as carbon dioxide alone.
Sometimes, the whole rise of world temperature in recent centuries (indicated by receding glaciers as well as available thermometer records) since the industrial revolution has been, perhaps more plausible, attributed to the increase of carbon dioxide. However, even this case seems more than doubtful when we examine the longest actual thermometer records.
The great oscillation of the prevailing temperature level amounting to almost 1.5 degrees in the 10-year means, that affected much of Europe, as well as Iceland, and perhaps wider regions of the world, between about 1690 and 1740—by far the greatest change in the record—cannot be explained by carbon dioxide changes or any human agency. It may be, but cannot be proved, that changes in the amount of volcanic activity or a fluctuation of the Sun were the dominant influences. Whatever models we produce must express a balance between the influences at work and their possible interactions.
h/t Bishop Hill