Caribbean climate in the future :Results from the PRECIS RCM Dr. Michael Taylor

A Future Caribbean Climate from PRECIS Michael A. Taylor and Jayaka D. Campbell Climate Studies Group. Mona Department of Physics University of the West Indies, Mona

Today

2080’s Industrial sized AC unit Large Water Storage Tank Support Wires Additional Foliage

2080’s Industrial sized AC unit Large Water Storage Tank Support Wires Additional Foliage

Why? Why the need for any change? Why the need for these changes? Why do we think Caribbean climate will change at all? What does PRECIS suggest the future Caribbean climate will be like?

The earth has warmed over the last century Why a change? 'Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.' 'Most of the observed increase in globally averaged temperatures since the mid- 20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. - IPCC (2007)

The earth has warmed over the last century Why a change? 'Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.' 'Most of the observed increase in globally averaged temperatures since the mid- 20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. - IPCC (2007)

Caribbean climate seems to be changing too. Why a change? # Warm days and nights are increasing!! # Cool days and nights are decreasing!! Peterson, T. C., M. A. Taylor, et al., 2002: Recent changes in climate extremes in the Caribbean region, J. Geophys. Res., 107(D21)

The earth will likely continue to warm Why a change? For the next two decades a warming of about 0.2 o C per decade is projected for a range of SRES scenarios. Even if the concentrations of all greenhouse gases and aerosols had been kept constant at year 2000 levels, a further warming of 0.1 o C per decade would be expected. - IPCC (2007) Projected surface temperature changes for the early and late 21st century relative to the period 1980 to The left and right panels show the AOGCM multi-model average projections (°°C) for the B1 (top), A1B (mmiddle) and A2 (bbottom) SRES scenarios averaged over the decades and

The earth will likely continue to warm Why a change? Global climate modeling (computer based simulations) has advanced significantly. The global climate models (GCMs) are run for varying storylines (scenarios) into the future to produce pictures of the future climate. Storylines grouped in families according to emphasis of storyline and emission gases produced. Projected surface temperature changes for the early and late 21st century relative to the period 1980 to The left and right panels show the AOGCM multi-model average projections (°°C) for the B1 (top), A1B (mmiddle) and A2 (bbottom) SRES scenarios averaged over the decades and B1 A1B A2

The global models suggest Caribbean climate will change as well Why a change? The GCMs can give a good first guess about what is likely to happen in the Caribbean. BUT Resolution is coarse so Caribbean islands often not represented. Nonetheless GCMs suggest that Caribbean not immune to the climatic changes that rest of globe likely to experience. We must adapt!!! Model-simulated temperature/ precipitation response to forcing scenario. Scenario is depicted by colour of the point (A1FI - red, A2 - grey, B1 - green and B2 - violet). Ovals show 95% Gaussian contour ellipses of the natural internal tridecadal variability. Hotter Wetter

PRECIS provides a little more detailed look on the future Why this change? PRECIS is a regional model (15 km - 50 km). Run over a Caribbean domain exclusively Forced at boundaries by GCMs Performs reasonably well with current climate. Run for a time slice in the future ( ), A2, B1 and B2 scenarios Run for baseline ( ) to evaluate change. Done as part of a collaborative project (Cuba, Belize, Barbados) Heard about PRECIS in previous talk, won’t repeat the model details. On this basis of the PRECIS results I am modifying my dwelling structure!! Why this change?

Temperatures Why this change? Irrespective of scenario the Caribbean expected to warm. Warming between 1 and 5 o C Warming greater under A2 scenario. Warming consistent with projections for other parts of globe.

Temperatures Why this change? Warming is year round. Nowhere and at no time in the year is the Caribbean cooler than present. Summer warming greatest. Under A2 warming up to 5 o C in larger islands Sea surface temperatures also warmer DJF JJA

Rainfall Why this change? For both scenarios Caribbean is in general drier. Up to 30% drier. Drying more severe under A2 scenario Far north Caribbean however could be wetter

Precipitation Why this change? Southern Caribbean dry year round. Far north Caribbean wetter between December and March Drying in late season (when normally get most rain) most severe. DJF JJA

Climatology Why this change? Still retain the climatology – e.g. MSD All months hotter and drier than baseline in both scenarios. JJA and SON indistinguishable Early and late season peak in rainfall identical Today January MSD Future Wetter Hotter

Vertical Shear Why this change? Annual SON In the mean there is stronger shear in main Caribbean basin, particularly across the main development region (MDR) In wet season, the change in shear is positive and high. Pattern consistent with rainfall changes. Pattern for A2 most severe. Strengthening at lower levels evident (not shown)

Cloud Cover Why this change? Jan Sept General reduction in cloud cover year round in main Caribbean basin. Pattern consistent with rainfall changes. Reduction for A2 most severe.

But before you build… Why this change? Hotter Wetter Windier Less cloudy 2080’s

PRECIS represents one set of model realizations Some provisos! Remember that PRECIS is forced by one GCM (Hadley Centre). Until we have other GCM data to force PRECIS, this at least gives us an idea of what to expect. This is one of the reasons for doing multiple scenarios i.e. A2 B2, etc. Future results expressed as range We can also take the consensus of the runs.ALLONE NONE

There is natural variability Some provisos! We must always remember that our climate system does vary naturally (i.e. has cycles of hot and cold, dry and wet). Must attempt to separate the climate change signal from that which might have occurred naturally. Precipitation Change (B2) – Annual Mean

There is natural variability Some provisos! We must always remember that our climate system does vary naturally (i.e. has cycles of hot and cold, dry and wet). Must attempt to separate the climate change signal from that which might have occurred naturally.

There is natural variability Some provisos! We must always remember that our climate system does vary naturally (i.e. has cycles of hot and cold, dry and wet). Must attempt to separate the climate change signal from that which might have occurred naturally. Temperature Change (B2)

There is still lots to do Some provisos! PRECIS is a good start but…. Doesn’t tell about sea level rise Need to analyse extreme weather in PRECIS e.g. Hurricanes Need more details about changes to Daily extremes Other significant climate variables to be analysed.

Conclusions PRECIS offers a glimpse into the future Caribbean Climate. PRECIS simulations done for the A2 and B2 scenarios. By 2080’s Caribbean 2-5 o C warmer. Warming everywhere, and year round. By 2080’s Caribbean generally drier. Drying more severe southern Caribbean and during peak rainy season. By 2080’s cloud cover is less than present. By 2080’s winds stronger.

Final words Remember the provisos. If changes are inevitable (as thought) there is need to mitigate and adapt. PRECIS Future data can be accessed via web: Some of these results are presented in a publication entitled: Glimpses of the Future: A Briefing from the PRECIS Caribbean Project.

Thank You