Why we have to face up to climate change

GENEVA, 30 November 2015 - Alasdair Hainsworth’s main claim to popular fame may be his decision to add the colour purple to the palette of the Australian Bureau of Meteorology to capture the possibility of temperatures reaching 50°C or more in the heatwave of 2013.

It didn’t quite happen. Though many records were broken that summer down under, the mercury did not rise above 49.6°C but all bets are off on what might happen now as southern Australia faces up to a blistering season in the sun fuelled by climate change and the El Niño weather phenomenon.

He was working then as Assistant Director of Hazard Prediction Services and is now Chief of Disaster Risk Reduction Services at the World Meteorological Organisation which he joined four months ago.

As COP21 gets underway in Paris, Hainsworth is fervent about the need for action to be agreed which will stem the rise of greenhouse gas emissions in a world where we are now permanently above 400 parts per million for CO₂ emissions.

“It’s a very, very serious increase in the amount of CO₂ in the atmosphere since pre-industrial times and that means there is additional carbon in the atmosphere that wasn’t there before which will retain heat in the atmosphere. It’s a warming blanket.

“Heat allows the atmosphere to retain more moisture and that translates into potentially more severe weather events. There is also greater potential for more significant thunderstorms and more intense tropical cyclones. Moisture in the atmosphere is basically the fuel for tropical cyclones and if there is more moisture and warm air available to them we are likely to see them become more intense and we are likely to see them in areas where we have not seen them before.”

While adding the proviso that no single weather event can be attributed directly to climate change, Mr. Hainsworth remarks that it is interesting to note that there is no precedent for two tropical cyclones hitting Yemen as happened in November with cyclones Chapala and Meghna. Similarly, it was also unusual to see a tropical cyclone moving through the Solomon Islands in the month of July.

He also comments on the remarkable rate of storm intensification observed in the cases of Tropical Storm Erika which inflicted significant losses on the Caribbean island of Dominica in August and Cyclone Patricia which was declared the strongest storm system ever to make landfall on Mexico’s Pacific coast in October.

“There was also a very dramatic intensification of a cyclone in the Coral Sea in Australia earlier this year, “ he adds.

Looking towards COP21, Mr. Hainsworth observes that unfortunate milestones have already been reached. “CO₂ is now 400 parts per million and that was seen as a significant threshold. We are now half-way towards the two degree rise in global temperatures that scientists have set as a threshold beyond which we will start to see irreparable changes taking place and more extreme events.”

The on-going decline in Arctic sea ice is also a serious cause of concern. September saw the third smallest ice pack on record. The minimum extent of Arctic sea ice in 1980 was 7.8 milliion ss kms and this year it was recorded as 4.6 million sq. kms. Global sea level rise since 1900 has been about 19 cms.

“The concern is not so much the sea level rise as it is the reduction in the amount of ice there to reflect sunshine away. As soon as you have that dark water which does not reflect back much of that radiation then you have a positive feedback loop. Instead of becoming a net reflector, if you remove this ice cover you trigger a process which could lead to disruption of major ocean currents and their normal circulation.

“When sea water freezes, the ice basically consists of fresh water and the salt is left behind, so underneath the ice you have really cold saline water. That water drops to the bottom of the Arctic Ocean and is one of the key drivers of the deep ocean currents which circulates sea water around the world.

“If you start to remove that ice and this water starts warming it can have a profound effect on our climate, and we don’t know enough about that yet. We don’t know how much it takes to stop those currents and what would happen in the event that they are disrupted.”

There are concerns that such a process could eventually lead to disruption of the Gulf Stream.

“These are the unknowns that we need to know more about and we need to investigate more. It is in order to prevent us getting to that point that a positive outcome is needed from the climate change talks.”

Looking towards the more immediate, short term hazards that communities face, Mr. Hainsworth says that given the potential hazards posed by the third strongest El Nino to date, there is a need to continue with the development of early warning systems that provide us with warnings of impending high impact weather events.

He says that by focussing on likely disaster impacts in weather warnings and forecasts rather than the technicalities of the situation this will assist in getting the message through to communities to take the appropriate action. This is an approach that is being adopted by more and more national meteorological offices.

He recalls that following the category 5 Cyclone Pam which hit Vanuatu in March this year, it had been noted that some people had said that they had no real appreciation of what a category 5 cyclone implied in terms of possible damage and loss.

Returning to the subject of COP, he says “we are setting heat records at around three times the rate we are setting cold records. There are signs definitely that things are changing and we’ve got to start taking notice of it. The COP21 is really very, very important.”