Comments on: Can we say climate change ’causes’ extreme weather events?

By: John Magrath

John Magrath — Mon, 19 Oct 2009 11:42:38 +0000

I’d just like to say thanks very much for 4 excellent comments. I was asked recently in an interview about climate change + earthquakes etc and I scorned the idea…maybe I need to look a bit more deeply. I cut a bit out of the blog re forest fires so just to say then that it’s pretty clear heatwaves are increasing e.g. across the Mediterranean, California, Australia, South Africa – and that increases the likelihood of forest fires. But, again, there’s plenty of examples of forest fires deliberately caused (arsonists or land grabbers), and conversely examples of how to manage forests differently to reduce risk/spread of fires. Might become a big issue for urban areas.

Stefano – yr comments about frequency are particularly apt. As agencies we’re very good at responding to severity of events (or what we perceive to be severity) – the big punches; but what can be more damaging and concerning to poor people may be frequency (of fairly small ones) – all the body punches if you like….Samuel Hauensteinswan at Action Against Hunger Uk has done some interesting research in Mali. Farmers there say drought is the most severe risk – but contrary to what outsiders might think, it’s pretty rare…what farmers hate are the neglected disasters: firstly high velocity, scorching Sahara winds – so- called “red winds” – said to be much stronger and more frequent nowadays – and secondly, sand that smothers everything (linked to deforestation). These 2 are nearly as severe as drought but much more frequent, and rather off the radar for government and agencies. And people are more vulnerable to these calamties than to drought.

By: James Eliscar

James Eliscar — Sat, 17 Oct 2009 23:07:38 +0000

Thank you Duncan for this briefing. I will start by saying that, climate change is not to blame for these events. However, it is evident that climate change is to blame of the increase in scale in which these events are happening and the scale of geography which they cover. We used to have –more or less, a regular cycle of such events happening yearly, or some of them once in a while. But now with climate change one event triggers another or amplifies its magnitude resulting in devastating effects. That, we can certain blame climate change. But most of all, WE have to blame OURSELVES. We get the globe off balance.

By: Pete

Pete — Fri, 16 Oct 2009 14:51:32 +0000

Thank you for a thorough posting that doesn’t keep to the populist line of climate change (presumably due to CO2) being the sole cause of all problems. Recently I’ve rarely seen deforestation blamed for changes in regional weather and flooding despite the effect that changing ground cover will have on local temperature, wind patterns and absorption of water.

I hope the development and environmental communities can keep pressure up to act to reduce CO2 usage now without needing to blame current disasters on climate change. Especially as some scientists are now saying that over the next 10 years global temperatures are likely to fall (before they rise even faster). We need to keep our creditability with accurate messages rather than losing it in the long term to have better headlines now. The message on vulnerability is very important.

NB The possible link between climate and earthquakes and volcanic eruptions was interesting. While these are each destructive events, the underlying build up of stress due to plate tectonics should be constant. This means that the more frequently earthquakes and volcanic eruptions are triggered, the smaller each one should be – might climate change diminish these natural disasters??

By: Olivia Ball

Olivia Ball — Thu, 15 Oct 2009 11:03:44 +0000

And what about earthquakes, volanoes and tsunamis? I’m no climate skeptic, but I thought ’surely not,’ until I read this: http://www.newscientist.com/article/mg20327273.800-climate-change-may-trigger-earthquakes-and-volcanoes.html

Meanwhile here in SE Australia we are preparing for another killer fire season. They have already started in Queensland, NSW and Broome (WA). Last season was terrifying.

By: Stefano B,, Italy

Stefano B,, Italy — Thu, 15 Oct 2009 07:45:06 +0000

Great briefing.

Considering my reminiscences of hydrology, I would say that the main effects of climate change on extreme weather events are connected with 2 concepts:
1. return period
2. vulnerability

1. return period
Return period is an estimate of the interval of time between events (like floods or heavy rains) of a certain intensity or size, and it is used to dimension structures so that they are capable of withstanding an event of a certain return period (with its associated intensity). (thanks Wikipedia).
What happens (or so it seems) is that climate change affects (reduces) the return period of extreme events: generally speaking this doesn’t mean than (for instance) it rains more (on aggregate), but that when it rains the chance that the event is extreme are higher (it rains more in a given – and short – interval of time)
2. vulnerability
The same event has different effects depending on the part of the world where it takes place: this means that the reduction of return period has much more effect on vulnerable environments (ex. big cities of developing world where – for instance – drainage and/or sewage networks are not present or under developed, coastal areas, etc etc..)

Sorry for my bad English,
Stefano