20 Nicholls Tues 1400 1530 NEIL PLUMMER
Yes, I guess weather and climate go hand-in-hand with risk and opportunities for primary
industries. When history stops repeating-- so, once upon a time we'd just talk about this
incredibly variable climate of Australia, but-- as we know-- things have shifted in recent decades.
And things are likely to shift further in the future in terms of climate.
So I'm going to talk about changes, recent changes, to our climate. I'm going to talk about some
of the scientific and modelling advances that have been made in recent years to help us better
handle climate, some new tools, products, and services, what's lying ahead in the decades-- the
decades ahead-- with climate change projections, and then finish with a short video about our
awesome climate outlook.
And just in case I forget, when this was prepared a week or two ago I didn't have at hand the
information that's come in the last few days. That it's just sort of tilting again slightly towards an
El Nino-like condition. So we thought we'd dodged a bullet last year-- despite it being very dry
over large parts of the east-- but there are just some things nudging towards El Nino.
So let's start with the changing climate, the temperature, rainfall patterns. I mainly want to focus
here on what's happened the past few decades over southern Australia. So the map on your righthand side shows, over the last 20 years, where we've had above-average rainfall over the north
and over the centre of Australia.
But in the south-- where it has been a lot drier than what it has been historically over the past 100
years or so-- in the southeast over that 20-year period we have a drop in rainfall in the lateautumn, early-winter period. Over the southwest, an even more significant change, and that
change-- as you can see in the time series on the bottom left-- goes back to around about 1970.
And characterised there is not just a drop in average rainfall, just the absence of really wet years
we've had in that southwestern region.
So we've got the data. The data is pretty clear here on the trend. Some significant changes there.
If we look at the reasons why we've seen those changes, we look at the atmospheric circulation
patterns. You see over southern Australia there's been an intensification of high-pressure systems
through there-- what we term the subtropical ridge.
And with that happening, the cold fronts and the low-pressure systems are being pushed further
and further to the south of the continent. So more rain has fallen over the ocean than what it has
over the south of the continent. And it is those global climate models that give us some insights
to what's driving those changes, and the most consistent pattern of change that comes out of
those models is when you force those models with natural variability, with increasing greenhouse
gases, and also decreasing stratospheric ozone.
So there is a human influence on the changes from the evidence from the global climate models.
That's particularly the case in the southwest. What's happening in the southeast is a much shorter
period, so that link is fall less robust.
That's the rainfall. We've seen an increase in temperatures of about a degree over the past century
or so. Most of that warming was occurred over the past 60 years, but the really interesting thing
is if you look at the extremes. And this is a measure of extreme temperature looking at a
frequency combined with a spatial extent. So I won't go into the details here, but very clearly it
shows, over the past 50 years or so, we've had a lot more of these hot events compared to the
earlier part of the record.
Of course, these extremes link into heat waves, to bushfire events, demands on water, and so
forth. What I find really interesting to ponder here is what lies ahead in the decade or two that
follows, because we've obviously seen some really extreme years-- some really extreme
summers-- that have popped out in recent years, and I guess the way things are trending with
what the model suggests is that these extremes are likely to continue over the next few decades.
I'm going to go from climate, just briefly, to weather forecasting, and talk about the science of
modelling and some of the advances that have been made over the past few decades. Weather
forecast models have got a lot more accurate, and don't be fooled by the curves here. The
decreasing lines mean trends towards more skillful forecasts.
So we've seen those in one, two, three, five, seven day forecasts. So that's through improved
science, that being translated into improved weather prediction models, better supercomputers,
better use of satellite data, and so forth. But there has been some rapid advances, and that kick
you see around 2010, there, was a real upgrade to the bureau's weather forecasting model.
We've seen some similar improvements on the seasonal forecast in time-scale, but not quite as
marked, and seasonal forecasting is quite a few decades behind weather prediction in terms of
the science and modelling. But on the left-hand side we have a skill plot from our dynamic
seasonal forecast model compared to the statistical model that we used just a few years ago. So
we've seen clear improvements and primary industries has funded a lot of this work, particularly
through the rural RDCs and the Managing Climate Variability Programme.
So agriculture's been an investor in these sort of models. We get some insights from overseas. So
there's many other countries that are doing similar work to us. The UK, who have now gotten
models down to 60 kilometre resolution as opposed to our 250 kilometre resolution here. They're
seeing some really significant improvements in skill, so we're looking to follow on that path.
So that's the back end of our seasonal that prediction system. Middle of last year we went
through an upgrade on the front end. So we it talked to farmers. We talked to a lot of leaders in
agriculture about what they'd like to see from improved seasonal forecast service.
We improved the interface. Not only did we have the three-month outlooks, but we looked at the
monthly outlooks, too. We introduced some more fine-tuned products such as that one there.
Looking at the chances of getting certain rainfall events over the next season, and we introduced
a lot more contextual information, such as videos, and I'll show the video right at the end.
A lot more of users of weather and climate information are going to mobile or tablet sites. So
we've made some efforts in that space, too. We do the weekly time scale really well. We've been
doing that for many, many decades. The last 20 years we've been doing the seasonal, and then
more recently we've popped into the monthly time scale.
There's still that gap between the one week and the month. So it's that multi-week time scale, and
this is work that's being funded through Managing Climate Variability Programme-- looking at
what skill do we have on that multi-week time scale. And we're seeing some really good results,
particularly with regard to temperature extremes.
And there's an example on your right-hand side looking at the forecast temperature for a twoweek period in January of last year. And then on the left-hand side compared to what was
actually observed. Now don't keep that up too long because you'll start to find where the model
didn't do so well.
The weather forecast interface. So this is a MetEye application. You'll find this on our website.
You can get a lot more detail, a lot more finer scale, for weather forecast information now.
And I find this one a bit like YouTube. You get on there and you can stay for hours playing
around, but really sophisticated. In this case, just drilling down into individual location and
what's the wind forecasted for the next week, there.
So improved visualisation, more forecast location, better accuracy because of the model
improvements I was talking about earlier, and quite extensible now, this particular system. We
provide a lot more stuff freely available on our website now, but we know there is a need-particularly for those in agriculture that want to use our information in a more risk-based
approach-- is that closer engagement with us to help do so.
So we find ourselves now giving a lot more briefings, specific training-- particularly with
agriculture-- and, in time, looking to what can we do more, forecast-wise. How can we help
forecast on specific events? It may be, the next five days, what's the likelihood of getting certain
threshold values?
And likewise taking that out on the weeks-to-season time scale. And, by and large, this isn't a
science push, here. It's looking from a user perspective. What are those risks and opportunities
that these products and services can better help with?
So recent updates to climate change projections. So, again, this is work that the bureau has been
doing now for quite some time with the CSIRO, and I'm really just going to show one slide, here.
Your right-hand side are temperature projections-- and, again, this is looking out much further, to
the end of the century-- and the two different greenhouse gas emission pathway is shown for
both temperature and rainfall. On your left-hand side-- on the far left, there-- is an emissions
scenario where emissions basically level off quite quickly over the next decade or so. And the
one right next to it where just emissions keep rising.
So obviously, on that rising emission scenario, we see some very significant changes in
temperature towards the end of the century. But there are significant changes regardless in the
decades ahead. But looking at around about three to five degrees out towards the end of the
century.
The rainfall changes were a bit less clear. And, again, low-emissions scenario versus the highemissions scenario. But a fairly clear-- particularly with the high-emissions-- this signal of
reduced rainfall over southern Australia, particularly in the southwest. And that appears to have
been borne out in the observations which I showed earlier.
I'm now going to stop talking and hand over to Doctor Andrew Watkins. We now do videos
every month. Some of you might have seen this video on Landline, which is shown on Sunday. It
goes for about three or four minutes, so please enjoy. I hope it works.
[INSTRUMENTAL MUSIC]
Welcome to the climate and water outlook for Autumn 2015. Neutral insight conditions are
likely for the next couple of months, but El Nino still can't be ruled out for this winter.
Now, temperature outlooks point towards a warmer autumn while rainfall outlooks suggest we
shouldn't bank on an early autumn break. But first, let's look at recent conditions.
Parts of southern Australia only had half their usual summer rainfall. Perth had a long dry spell-61 days without a drop of rain-- but many areas had a wetter than expected summer. For inland
Australia, much of that rain came in the first two weeks of January.
These January rains meant some regions saw a rise in their soil moisture. However, many areas
still have dry, deep soils. This means drought conditions persist, particularly in Queensland and
Western Victoria. While both states had summer rains, unfortunately not enough fell in the
places that needed the most.
Summer felt cooler in the east than in recent years, mainly due to fewer days of extreme heat.
But daytime temperatures were actually average to warmer than average.
In the west, WA had one of it's hottest summers on record. Setting records for the latest 49
degree day and Australia's hottest February night. The hot and dry set the stage for bushfires to
rage in the southwest for weeks-- so long that fire fighters from other states flew in to offer
relief.
The tropical cyclone season had a late but dramatic start. Only twice on record have we gone so
far through the season without a coastal crossing. On the 20th of February, two cyclones made
landfall. TC Lam hit the top end at category IV. Then, just hours later, TC Marcia crossed the
Queensland coast at category V-- the strongest on our scale.
Looking ahead, let's see what may drive our climate in the coming months. Our ENSO tracker
remains at neutral. However, several models suggest the tropical Pacific Ocean may once again
shift towards El Nino by the winter.
Model accuracy isn't as high at this time of year, so we'll be keeping a close eye on any further
developments.
The other key driver in autumn and early winter is this location of the high-pressure systems,
known as the Subtropical Ridge. In recent years, the highs have been further south. That has
made it harder for fronts and weather systems to bring rain to southern Australia, as shown by
the orange and red areas on this map.
Turning now to the rainfall outlook for autumn as a whole, wetter than average conditions appear
likely in northern Western Australia and also Central Australia. But if we focus in on March,
odds favour wetter conditions for parts of Queensland and northern New South Wales, but these
odds weaken for the southern states. Given the long-term trends in southern Australian rainfall,
this suggests an early autumn break is less likely. These outlooks both have moderate accuracy.
In terms of streamflow, the January rains are now heading down some of our water ways. The
February to April streamflow outlook suggests low flows are likely at 27 locations, median flows
at 25, and high at just six. Accuracy for your streamflow forecast is high at this time of year.
Moving on to temperature, the outlooks for autumn indicate warmer, on average, days and nights
for most of Australia. Accuracy for these outlooks is moderate to high at this time of year. With
the warm and dry persisting past the end of summer, bushfire risk remains for southern Australia.
So, in summary, a warmer than normal autumn and an early break looking less likely. Low to
median streamflows are expected across eastern Australia. Bushfire risk remains for the south,
and cyclones remain possible in the north.
For more details, head to our website at bom.gov.au/climate/ahead. Our next video will be
released on Thursday, the 26th of March. For the Bureau of Meteorology, I'm Andrew Watkins.
[INSTRUMENTAL MUSIC]
So thank you, Andrew. If Andrew hadn't done-- as I said earlier-- if Andrew hadn't have done
that video this week, he would have been talking up the chances of El Nino just a tad, here, so
don't be surprised if you see-- on that ENSO tracker-- the dial, perhaps, shift a little bit. There's
current deliberations around that going on in the bureau now. So thanks very much for your time.