Tropical cyclones projection over the Southwest Indian Ocean under different extents of global warming

Enhanced IR image of four tropical cyclones at 1200UTC 22 Feb 2007 in the South West Indian Ocean. [Source : US Navy/NRL/ (c)EUMETSAT 2007]

The Paris Agreement achieved in December 2015 established that the signatory countries should pursue to hold the increase in global average temperature to below 2 °C relative to the preindustrial period and to strive to limit the temperature increase to 1.5 °C below the preindustrial period. A recent study by Muthige et al., 2018 used the Coordinated Regional Downscaling Experiment-Africa regional climate models to downscale six global climate models of the Coupled Model Inter-comparison Project Phase 5 to high resolution. This serves towards studying changes in tropical cyclone tracks over the Southwest Indian Ocean under different extents of global warming (1.5 °C (Fig.3), 2 °C (Fig.4) and 3 °C (Fig.5) of warming with respect to preindustrial conditions). The results projected that the number of tropical cyclones making landfall over southern Africa under global warming will decrease, with 2 °C being a critical threshold, after which the rate of cyclone frequency with further temperature increases no longer has a diminishing effect. Fewer cyclones may bring benefits and reduce damage to the southern African region. Although a decrease in damages associated with flood events is desirable, general decreases in tropical cyclone and tropical lows may also be associated with decreased rainfall over the Limpopo River basin and southern, central and northern Mozambique (with negative impacts on dryland agriculture).

Figure 2. Modelled frequency of tropical cyclone-like vortice centres at a 2° spatial resolution and six hourly temporal resolution under present-day climate (1971–2000); obtained from six different CCAM downscalings under RCP8.5.

Figure 4. Simulated change in the frequency of tropical cyclone-like vortices per 2° grid point across six downscalings under 2 °C of global warming. The area where the changes are significant are indicated by crosses.

Figure 3. Simulated change in the frequency of tropical cyclone-like vortices per 2° grid point across six downscalings under 1.5 °C of global warming. The area where the changes are significant are indicated by crosses.

Figure 5. Simulated change in the frequency of tropical cyclone-like vortices per 2° grid point across downscalings under 3 °C of global warming. The area where the changes are significant are indicated by crosses.

Journal Reference:

Muthige, M.S., Malherbe, J., Englebrecht, F.A., Grab, S., Beraki, A., Maisha, T.R. and Van Der Merwe, J., 2018. Projected changes in tropical cyclones over the South West Indian Ocean under different extents of global warming. Environmental Research Letters, 13(6), p.065019.

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© 2018 Oceanographer Daneeja Mawren