¶10 Understanding of the recent slowdown also built upon prior research into the causes of the so-called big hiatus from the 1950s to the 1970s. During this period, increased cooling from anthropogenic sulfate aerosols roughly offset the warming from increasing GHGs (which were markedly lower than today). This offsetting contributed to an approximately constant global mean surface temperature (GMST). Ice-core sulfate data from Greenland support this interpretation of GMST behaviour in the 1950s to 1970s, and provide compelling evidence of large temporal increases in atmospheric loadings of anthropogenic sulfate aerosols. The IPO was another contributory factor to the big hiatus13.
that fuels our climate system.
Thus a cooling trend in the GMST and the global system.
¶11 Research motivated by the warming slowdown has also led to a fuller understanding of ocean heat uptake. … In summary, research into the causes of the slowdown has been enabled by a large body of prior research, and represents an important and continuing scientific effort to quantify the climate signals associated with internal decadal variability, natural external forcing and anthropogenic factors.
¶13 Recent claims by Lewandowsky et al. that scientists “turned a routine fluctuation into a problem for science” and that “there is no evidence that identifies the recent period as unique or particularly unusual”26 were made in the context of an examination of whether warming has ceased, stopped or paused. …
¶15 … Just exactly how such changes should be referred to is open to debate. Possible choices …
¶18 "Superimposed on this forced anthropogenic response are small signals of solar irradiance changes, cooling and recovery from volcanic eruptions and internal variability.”
¶21 The big hiatus and warming slowdown periods correspond to times during which the dominant mode of decadal variability in the Pacific—the IPO—was in its negative phase. …
¶22 … Newly identified observational errors do not, however, negate the existence of a real reduction in the surface warming rate…
¶24 Research into the nature and causes of the slowdown has triggered improved understanding of observational biases, radiative forcing and internal variability.
“It has been claimed that the early-2000s global warming (b) slowdown or hiatus (a)(e), characterized by a reduced rate of global surface warming (c), has been overstated, lacks sound scientific basis, or is unsupported by observations. The evidence presented here contradicts these claims (d).”
Fyfe et al. 2016: stamp collecting vs informing and clarifying. Examining a failure to communicate... a question of perspective.
Appreciating Earth's Climate
and senior fellow at the Woods Institute for the Environment,
unpacks the political and scientific debates surrounding climate change.