A Significant Difference: 1.5 °C versus 2.0°C in the Climate Change Battle

By Susanna De Beauville-Scott, Department of Sustainable Development

THE difference between 1.5 degrees centigrade (°C) above pre-industrial levels and 2°C above preindustrial levels may come across as insignificant in terms of the mathematics. However, in reality, the difference of 0.5 degrees can be the difference between life and death for us as small islands.

Limiting peak warming close to 1.5 °C by mid-century will still result in significant damage. According to the Intergovernmental Panel on Climate Change (IPCC) and the World Bank’s “Turn Down the Heat: Confronting the New Climate Normal” report, risks to unique and threatened systems, such as coral reefs, are high at 1.5 °C and sea-level rise will continue long after 2100. Further, even with the most aggressive mitigation action and limiting peak warming close to 1.5 °C, there will still be substantial damages in the form of extreme heat events, damages to water resources, and risks to food security.

Note that, generally, a small anomaly of 1-2 °C for about 5-10 weeks will induce coral bleaching. We have direct experience with this in the region. Further, even if corals do not bleach, their reproductive organs can be damaged by warmer water. Corals also produce few reproductive organs (both eggs and testes) in warmer waters.

The IPCC notes that at 1.5 °C, we stand to lose about 50% of coral reefs. However, at 2 °C, we stand to lose well over 50%. Note that these figures do not take into consideration ocean acidification and existing stresses, such as pollution on coral reefs.

In 2005, a bleaching event occurred after a prolonged warming period of about 1 °C. In Saint Lucia, surveys showed that 50-80 percent of corals along the west coast bleached. Interestingly, given other stresses, such as pollution, to date many of these coral reefs have not fully recovered.

In that same year (2005), it was also noted that the white sea urchin (Tripnuestesventricosus) showed no sign of recruitment and the dolphin fish (mahimahi) catch was unusually low. It is hypothesized that the warmer water also affected these species.

Interestingly, in 2005, the World Resources Institute informed that about 25% of visitors to Saint Lucia do so in part due to the island’s coral reefs. This Institute also sought to put a value on coral reefs in Saint Lucia. Their total estimate was US$188.5M-US$244.8M per annum (Coral reef associated tourism and recreation – US$160-194M; coral reef associated fisheries – US$0.5-0.8M; shoreline protection in avoided damages – US$28-50M).

Moreover, over 2,600 fishermen and their families depend directly on fishery resources in Saint Lucia. This accounts for 6-8 percent of the island’s population.

Thus, when Saint Lucia’s climate change negotiators, youth, musicians and others advocated for 1.5 °C in the Paris Agreement, it was a worthwhile battle and resulted in the Paris Agreement targeting a goal to “holdingthe increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change.”

The 23rd Conference of the Parties (COP) to the United Nations Framework Convention on Climate Change (UNFCCC) is coming up soon and negotiations will continue to ensure effective implementation of the Paris Agreement.

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