Extreme Weather Events: The New Norm?

Dr David JonesManager of Climate Monitoring & Prediction

Bureau of Meteorology

Acknowledge: CSIRO, BoM, IPCC, ACE CRC, Dep Climate Change & Energy Efficiency

Overview

• The big picture – global trends and the last few years.

• The last few years in Australia – an aberration or part of a trend?• Looking to the future of climate change.

• January 2009 heatwave (Vic & South Australia) – 374 excess deaths in Vic alone.

• February 2009, Black Saturday – 173 deaths, 414 serious injuries. Insured cost of ~$1 billion.

• August and November 2009 heatwaves – severe crop damage.• March 2010 Melbourne hail storm. Insured cost of ~$1 billion.• March 2010 Perth hail storm. Insured cost of ~$1 billion.• Inland flooding 2010/11: January NSW/QLD, September Vic, Oct

NSW, January & February Vic/Tas.• Queensland flooding 2010/11• Queensland coast – Maryborough, Rockhampton

December/January 2011• Darling Downs and west – January/February 2011• Brisbane – January 2011• Total insurance claims > $2 billion.• Tropical cyclone Yasi – strongest Queensland cyclone since 1918?

Extremes in the Last Few Years

Are Global Weather & Climate Disasters Escalating?

Count of weather disasters suggests so – from Munich Re (Neumayer and Barthel 2011)

“Weather” disasters

“geological” disasters

Is the Cost of Global Weather & Climate Disasters Escalating?

Hard to tell – changes in demographics, wealth and inflation (Neumayer and Barthel 2011)

Traditional Approach

Geographical Approach

Why Might we Expect a Trend?

400,000 years of data

Currently ~395 ppm (or ~460 e-ppm)

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)

Global Temperatures in 2010 (World Meteorological Organization)

+0.53°C warmest year on record,though a statistical tie with 1998 and 2005.

Global Rainfall in 2010 (NOAA)

~50mm above average – the wettest year on record → accelerating hydrological cycle, likely to give rise to more floods and more droughts.

Record High Sea Level (CSIRO)

Record high sea levels in 2009/10 → more coastal areas at risk of inundation, increased vulnerability to storm surges.

Tropical Cyclone Activity (FSU)

But, near record low levels of tropical cyclone activity around the planet.

• Direct effects of climate change on individual extreme events: e.g., storms, tropical cyclones & heatwaves

• Indirect (background) effects: e.g., sea level rise exacerbating floods, higher temperatures leading to drying of forest fuels, lower fuel loads (due to winter drying)

• Effects on resilience & preparedness: e.g.,– Rural depopulation due to drought less fire fighting

volunteers?– Uncertain return period for events (leading to over/under

investment in preparedness)– Non-availability of insurance or insurance too expensive– Uncertainty delaying or stopping investment decisions– Long-term drought (or perceptions of fire risk) damaging

rural economies

Climate Change Impacts – Extremes, Safety and Infrastructure

Australian Temperatures

Temperature has increased by about 0.7 C since 1960. 2010 rather cooler than recent years.

Changes in Maximum Temperature Extremes

Hot days becoming more numerous and cold less numerous

Australian Rainfall Trends

Increase in many parts of northern and central areas and decrease in the south and east

Cumulated Fire Danger

Melbourne Airport (“central Victoria”)Clear impact of warming and recent long-drought.

Start of the long dry

13 year drought

2010: Second Wettest Year on Record

One of the strongest La Nina. Possibly strongest since 1917/18 → record wet across north and east.

But record dry in the southwest?

Trends in Heavy Precipitation

2010 a record, but trend is very weak or non-existentDependent on threshold and dominated by variability.

Change in Australian Sea Level

Since the early 1990s, sea level rise has been 1 to 3 cm/decade in the south and east and 7 to 10 cm/decade in the north and west

Central Queensland CoastSea Level

~2.5cm/decade or ~9cm since the last major (1973-75) La Niña sequence.

y = 0.2083x + 2395.3

R2 = 0.028

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Linear (Rosslyn Bay,Queensland)

Tropical Cyclones

Yasi – strongest Queensland TC since 1918 and possibly 1899.

But no evidence of an increasing trend.TC numbers appear to be overall in decline, but a lot of uncertainty.

Number of severe tropical cyclones impact QLD

Projections for Australia in 2030 (CSIRO & BoM)

Warmer by 0.4 to 2.0°C 10-50% increase in days over 35°C 10-80% decrease in days below 0°C Up to 10% less annual rainfall in SE Australia Up to 20% less annual rainfall in SW Australia Up to 10% more summer rainfall on east coast Up to 10% more autumn rainfall inland Heavier rainfall where average rainfall increases or decreases slightly Increase in intensity of tropical cyclones

The Future Rapid Warming Expected

+1.7ºC

600ppm

+2.7ºC

850ppm

+3.2ºC

1250ppm

Warming will be largely dictated by CO2 emissions. Sea level rise and warming will continue for centuries.

Rainfall Changes

Rainfall change for 2090-2099 relative to 1980-1999.

Drying across southern Australia (and indeed most subtropical areas).

The Hydrological Cycle

Climate models and observations reveal a number of robust responses:

• Atmospheric moisture holding capacity rises rapidly with temperature – about 7%/degree

• Evaporation and rainfall increase globally – around 2%/degree

• The subtropics tend to dry – particularly in winter.→The average rainfall intensity rises, but the number of rain days tends to fall.→Droughts become more severe and floods become more severe→ Change in fire regimes

In Summary

• The last few years have been highly unusual:Record hot and dry drought in southeast

Australia;Record number of heatwaves;Record (?) number of heavy raindays;Two unusual storms – Perth and Melbourne;Strongest TC on Queensland coast since

1918 (or earlier); andRecord southwest WA dry

• Some changes are consistent with global warming – but for many there is not strong evidence to draw a link (yet).