A new study has claimed that we may breach the 2 degrees Celsius climate change increase threshold by the late 2020s — almost two decades earlier than current projections.
A huge issue in climate science is where to set the pre-industrial baseline, before fossil fuel burning kickstarted warming. Until the 20th century, ocean temperatures records were a sporadic and non-standardized patchwork of millions of observations collected by sailors to chart courses through seas.
The ratio of strontium to calcium at a particular part in a sclerosponge's skeleton decreases as ocean waters warm, enabling the scientists to measure 300 years of temperature records in cross-sections of their bodies — similar to reading tree rings. Their results suggest that warming began in the 1860s, about four decades earlier than the UN's Intergovernmental Panel on Climate Change estimates.
Troubled watersOther climate scientists have criticized the new study's findings. The researchers say they assumed that oceans are well-mixed and that the water temperatures recorded by the sponges came from depths that mainly respond to heating from the sun. Camille Parmesan, an ecologist at the University of Texas, Austin and a coordinating lead author for the IPCC's 6th Assessment Report, noted that the temperature of one part of the ocean is unlikely to represent ocean temperatures elsewhere."You cannot extrapolate from the Caribbean to the whole of the world's oceans," Parmesan told Live Science.