BOM Webinar recording: State of the Climate


Angela: Good afternoon everyone, welcome to our State of the Climate webinar. For those joining us for the first time welcome and
for anyone who joined us for our webinars before welcome back. Today we’ll be giving
you an in-depth look at the most recent State of the Climate Report released in late 2018
by the Bureau of Meteorology and CSIRO. My name is Angela and I am delighted to be your
moderator today. Clare is our producer and will help moderate your questions. Hi, Clare.
Clare: Hi, Ange. Angela: Please send them through via the chat
function and we will address as many as we can during the webinar, but before we begin
may I ask for your attention as we cover off some housekeeping items. Our broadcast today
will run for 60 minutes with plenty of time allocated for questions. This webinar is also
being recorded and the video will be shared with you via email. For first-time webinar
attendees please see some helpful tips on your screen. Please note the chat box where
you can send through any questions or feedback for the presenter. Please use this and not
the Q&A box to send your questions to us during the session and as I mentioned before we’ll
answer as many as we can during the allotted breaks. We do have a very high volume of listeners
today ladies and gentlemen and so we do apologize if we cannot address all questions during
the webinar. If the chat box is not visible on the right-hand side please open it using
the chat icon within your control panel. And at last I am delighted to introduce you to
our experts and lead authors of the report Dr. Michael Grose and Dr. Lynette Bettio.
Welcome Michael and welcome Lynette. Dr. Michael Grose is a research – oh, there you go! Good to
have you. Dr. Michael Grose is a research scientist at the CSIRO Climate Science Centre
in Hobart. His research focuses on the science of climate change processes, understanding
climate change as we have seen to date, and how we can produce future climate projections that
are useful for a range of stakeholders. He previously worked in marine and Antarctic
science and is the author of numerous research papers, book chapters, and stakeholder communication
products. Dr. Lynette Bettio is a senior climatologist in the Climate Monitoring Team at the Bureau
of Meteorology. She has a PhD in Climate Science. The climate monitoring section is responsible
for the preparation and analysis of Australia’s instrumental climate records. Lynette examines
and communicates on changes to Australia’s climate including long-term trends in rainfall
and temperature and the interaction with extreme events. Another focus is drought across Australia
and how the bureau can best communicate and inform around this. Welcome all, Lynette and
Michael great to have you with us. Who would like to tell us a little bit more about what
we’ll be covering today? Lynette: Thanks Angela and yeah, very happy
to be here. So I’ll start off today and just looking at our key messages from the report
so as you said our latest report was released in late 2018. It’s released every 2 years
and this is the 5th report of this series and really drawing on that latest climate
science, the latest research, the latest data to describe those changes and long-term trends
in Australia’s climate. So really important those trends that we’re seeing in previous
reports, they’re continuing in this report. So Australia’s climate has warmed by just
over 1 degree since national records began in 1910 and this is leading to an increase
in the frequency of extreme heat events. There’s also been a long-term increase in extreme
fire weather and fire season links across large parts of Australia since the 1950s.
Michael? Michael: Thanks very much, Lynette. So later
in the session I’ll be covering some content on oceans, greenhouse gasses, and future climate
and similar to the previous sections some of these key messages are basically a continuation
of things we’ve seen before. So oceans around Australia have warmed and again this is by
about 1 degree and this is contributing to longer and more frequent marine heatwaves
in several regions around Australia. Also sea level has continued rising. The increased
– the absorption of carbon dioxide from the atmosphere into the ocean is changing the
ph of the oceans. Global carbon dioxide in the atmosphere has increased to levels not
seen in at least 800,000 years and likely in the last 2 million years or more. Australia
is experiencing climate change and some of those changes can be attributed to human activity
right now and many impacts are being felt by communities and in industry sectors and
this report draws on the best available peer reviewed information from within CSIRO, the
Bureau, other Australian scientific organizations and around the world and presents multiple
evidence sources. Going to the next slide… To begin out webinar we’ll start with content
on temperature, rainfall, fire weather, and compound extreme events. These are on the
kind of land and atmosphere side of things. I’ll then give an overview of greenhouse gases
in the longer context and also what we measure here in Australia, then go on to talk about
what’s happening in the oceans and what we can expect from the future climate. Lynette: So I’ll start off and just talking – so just starting with this slide here so
it’s actually when we releases the report this is retweets of a tweet that we put out
from AFAC, and AFAC is the national council for Fire and Emergency Services in Australia
and New Zealand. So talking about how the report – it’s not just a report released on
the day, but that information is used to help inform our partners in Fire and Emergency
Services in this case, and government and organizations around Australia. So over 100
years of data – climate data included in the Bureau’s climate record just really helping
to inform decision making around the challenges of climate change and increasing extremes. So Michael’s going to talk more about greenhouse gas concentration later on in this webinar
but I just wanted to start here because it’s really the increases in atmospheric gases
such as carbon dioxide that’s really driving these changes. So as we can see from this
graph earlier on it goes up and down, it’s fairly regular cycle and in the last 200 years
or so we’ve seen that rapid increase in carbon dioxide in the atmosphere. So what changes
have we seen in response to that? So the changes that we’ve seen include changes in temperature. So we have here sea surface temperature in the oceans around Australia, and Australian
surface air temperature and looking at this graph we can see that it goes up and down
a lot, but we can also see a steady rise. So Australian climate is quite variable. We
see variations in our temperature and in response to things – climate drivers such as El Niño
and La Niña. So we see the up and down, but in more recent years we’ve seen that on top
of a warming trend. So the warming trend being the climate change part of that story and
the up and down being that variability and what we’re seeing over the land in Australia
is also reflected in the warming that we’re seeing in the oceans around Australia. So we’ve seen – I’ll just go back, so we’ve seen around a 1 degree warming in temperature and
so 1 degree, it doesn’t sound like a large number when you say 1 degree so I just really
wanted to talk to why does that 1 degree matter? And we talked about that 1 degree warming
in the introduction leading to an increase in heat extremes. So I just wanted to look
at this slide. This is one of my favourite figures for really explaining why that 1 degree
matters. So if you look at the curve, so if you think about that 0 where you see that
peak of the curve so this is describing how it changes from the average. So looking – if you think most of the information – most of – so describing temperatures we line all our
temperatures up from cool to very warm. So most of the temperatures are around average
and we have some very cool temperatures, and we have some very warm temperatures. I like
to – if I’m giving this to a room we can imagine our virtual audience, and if we lined
our virtual audience up and we had some short people, and we had some taller people I like
to think I’m pretty average height and I’d probably be in the middle with most people
around that average. So that curve that’s further to the left-hand side there, that’s
the 1951-1980 curve. So we can see that those curves have shifted a little bit further to
the right. So that’s just with that 1 degree of warming, that 1 degree shift. So if you’re
looking on the right-hand side there you can see it’s around that standardized anomaly
that number 2 there. So very warm events that only happened 2% of the time, or 1.97% of
the time for the period 1951-1980 are now happening 12.48% of the time. So real shift
in the frequency of those very warm events that we’re experiencing. So just that 1 degree shift in that average in the mean has really impacted on how often we’re seeing those really
warm events and those really warm events are often where we see the most impact from climate
change. So you don’t really feel a 1 degree change, or that mean change in temperature, but you really feel that impact of heatwaves and those very warm months. And likewise with
daily temperature this is another way to show how these extreme heat events are increasing. So with those what we’re seeing here is those daily means. So average over all of Australia
and we’re seeing that top 1% of those days compared to the month that it was recorded
in. So looking at 2013 which is near the right-hand side there which is that – sort of that highest
one over 28 those very warm, extreme days in 2013. So we can see towards the right of
the graph there’s been that real increase in frequency as we go through time whereas
at the start of last century with records starting in 1910 there wasn’t as many days
with those extreme temperatures compared to what we’re seeing now. So another area where our climate is changing, where we’re seeing those changes are changes in rainfall across
Australia. So there’s been that real shift of – one of the major trends that we’re seeing
is that drying shift across southern parts of Australia and this is especially evident
in that April to October period. So an important agricultural period for southern Australia
and an important period too for our water resources as we get much of our rain during
this part of the year. So what we’re looking at here is a graph of 20 year April-October
rainfall deciles. So taking those 20 years, those last 20 years and looking at how those
last 20 years compare to all the other 20 year periods that have gone before with national
records starting in 1900. So how did these most recent 20 years compare? So we can see that over large parts of southwestern Australia we can see lowest on record. So this most recent period has been lowest on record and that’s very much below average is that bottom 10%. So with the last 20 years for much of south-eastern Australia and southern parts
of Australia being in that bottom 10% of what we’ve seen compared to other period. So again with rainfall – so these graphs here are looking at the rainfall anomalies for southwest/western
Australia for April-October and the rainfall anomalies for southeast Australia for April-October
on the right-hand side there. And so what we’re seeing – you first look at this and
similar to temperature there is large variability in the rainfall that we’re seeing. So similar to temperature this is against the 1961-1990 average so we’re looking at the anomalies
around that average and we just have – we look at anomalies to see – to look at how
it changes with respect to that mean and what we can see with southwest Western Australia
there’s still – there’s large variability, but we can also see in the later part of the
period, so going more towards the right there we can see a decline in that rainfall received
since around the 1970s. So since around the 1970s for April-October we’ve seen around
a 20% decline in rainfall compared to the period before. And what we’re seeing too,
we’re not seeing those really wet years as we saw earlier in the period. So likewise in southeast Australia you see a similar decline in rainfall starting around the 1990s so this
is really associated with a shift in those weather systems. So with southwest Western
Australia during April-October getting a lot of its rainfall from those frontal systems
coming through and not seeing as many frontal systems from that period coming through. Clare: Can I ask a quick question, Lyn we’ve had a question from John. He said when you say south-eastern Australia what area are you talking about? Does it include the river
area of New South Wales? Lynette: It really includes that southern
part of New South Wales, Victoria, and some parts of South Australia, eastern South Australia
and Tasmania. I’ll – I can confirm that area and get back to you. It’s in our – it is in
the report so we can get back to you on that. But – so yeah, so southwestern Australia is
that smaller pocket NWA and south-eastern Australia over a larger region. and again
seeing that decline from around the 1990s so with southwestern Australia mainly relying
on that frontal rainfall for those anomalies, those rainfall coming through – sorry, of
that rainfall coming through and seeing a real decline in that rainfall is those frontal
systems that push further south. Now south-eastern Australia we get – I say we because I’m living
in Melbourne but southeastern Australia gets its rainfall from a lot of other sources.
So it’s seen a decline in that rainfall from those frontal systems but we get the tropical moisture
coming through from the northwest cloud band cut up loads which is also seeing a decline
but there’s other sources as well. So there hasn’t been – as a decline it’s more recent
than what we see in southwestern Australia. Yes, Clare? Clare: And Lynn please one more clarification from your temperature graph. David’s asking
us in the first temperature graph shown today what temperature represents the benchmark
on the graph that is the 0 on the X axis? Lynette: Yeah, sorry I realised as I explained the anomalies in rainfall that I didn’t explain
that the anomalies in temperature were taking from the 1961-1990 mean as well so we’re looking
at these anomalies in temperature there compared to the 1961-1990 average.
Clare: So he’s saying what temperature represents the benchmark on the graph that is the zero? Lynette: Yeah, so the zero is the 1961 average yeah.
Angela: Thank you. Clare: Thank you David, hopefully that’s clarified
things. Lynette: So another – what we’re also seeing in rainfall, so we’re also seeing across October-April in the rainfall again with that
20 year period compared to all other periods we’re also seeing more rainfall in northern
parts of Australia. We’re very much above average for the last 20 years. So we talked
about fire weather in the introduction so this is one area that’s a very active area
of study. So looking here at the Forest Fire Danger Index, so the Forest Fire Danger Index,
it takes into considerations the maximum temperature – the temperatures that we’re seeing, wind
speed, the humidity and the state of the vegetation so really we’re talking about the conditions
that are conducive to fire. So what we’ve seen, that these fire conditions are worsening.
So we’re seeing an increase in the length of the fire season and we’re seeing a more
intense – so more frequent, intense fire conditions. So this is largely seen across – we can see
on this graph here again across parts of south-eastern Australia we’re seeing an increase in those
fire weather conditions. So those conditions that are very conducive to bushfire weather. Angela: So Rob’s just quickly asked us large parts of South Australia are considered forest. Does the summary of FFDI also equate to grassland risk? Lynette: Again it does take into – it does take into account some consideration of the
vegetation but … this is – it’s done on a national scale totally using that single
measure. Angela: Thank you. Lynette: So one thing we looked at in the report is a compound extreme events. So we’ve talked about the trends in single variables. So we talked about trends in rainfall, trends
in temperature and these can often be considered to – we see such as fire weather that they
can combine to… produce those impactful and hazardous events, but compound extreme
events, they can also be events that happen within – simultaneously across a larger region
which may impact on your ability to respond to those events or it can be in time scales
again where you’re stressing the system and you have to respond within a certain time. So one example that we referred to in the report was that what we saw in Tasmania during
2015-’16 so those background warming trends and the background drying trends and that
natural variability as well impacts on top of that seeing the extreme heat and low rainfall
across Tasmania and then we saw a transition to record atmospheric moisture and heavy rainfall
in June in 2016. So just having a look at that and what that looks like on our maps
and these maps are available on the Bureau website. It’s part of what we monitor so Tasmania
is October 2015 again with those rainfall deciles. The dark red on the left-hand side
there being lowest on record for October and the very much low average being that bottom
10%. So large – much of Tasmania being lowest on record for October and again with the maximum
temperature highest on record and in the top 10% for much of Tasmania for October 2015
and really setting up those preconditioning for those bushfires that occurred during the
summer season. And then in June 2016 we saw record high rainfall. So on right right-hand
side there rainfall highest on record and very much above average across large parts
of Tasmania and this was associated with floods across Tasmania and just drawing your attention
there to the sea surface temperature anomaly that we saw in the Tasman again this is monitored
on the Bureau’s website and again it’s the anomalies with respect to a 1961-1990 average. So you can see that one that really sticks out there, that’s May 2016 so really a large
anomaly that we just hadn’t seen before compared to the years before. So I will pass on to
Michael then and he will go through the rest of the presentation. Michael: Thanks very much, so I’m going to go through first of all atmospheric composition
and concentration of greenhouse gases and then onto oceans and then finish on future
climate. So taking another look at this plot and putting the recent greenhouse – or concentration
of carbon dioxide in a very much longer context we can put the recent measurements which are
visible as a blue line right at the very far right of this graph going back through
time from the year 2000 through to the year 0 we can reconstruct what the CO2 concentration
was by looking at things such as ice cores. This is the bubbles trapped in ice in Antarctica
that make a natural record of what the carbon dioxide level was. And then jumping to the
left panel we very much stretch out the timescale to be hundreds of thousands of years before
the present so this is a very long ice core with a very long record going back much further. So just be very aware that those timescales are very different and you can see in the
much longer record there was cycles of carbon dioxide increasing and decreasing through
ice age cycles reinforced by what we call climate feedbacks, but the concentration of
carbon dioxide never really got above 300 parts per million and was averaging at about
280 parts per million as we came into the modern era. Then in the last 2000 years it
was fairly steady at about 280 or less parts per million of carbon dioxide through to the
recent time where it has been shooting up. And so just to put a little bit more context
on those timeframes and what they mean just bringing up the first little annotation Lynette… this is where our friends Homo neanderthalis kind of emerged, then Homo sapiens emerged,
and then just in the last little sliver of that broad plot is where we saw permanent
settlements and agriculture coming on for humans. So we know that carbon dioxide through
all this time was closely coupled to global temperature and we expect that relationship
to hold now and into the future. So this is work from the Australian Antarctic Division
together with CSIRO and other research organizations around Australia to reconstruct that carbon
dioxide back through time from Antarctic ice cores, and then more recent measurements. So going to the next slide… here’s the direct measurement of carbon dioxide concentrations
measured at Cape Grim which is in northwest Tasmania which is one of three global clean
air stations. There’s a network of more than that but these are the three most prominent
and important sites. The other ones are in Hawaii and in Greenland. And here you can see very much different types of colour than in the previous graph. Since the mid-1970s
we’ve seen a fairly steady increase in carbon dioxide concentration in that clean air, that
baseline air coming and hitting northwest Tasmania. You see a slight wiggle in the seasonal
cycle, but the trend is extremely clear. Going to the next graph here we can put together
the measurements at Cape Grim and the other air monitoring stations and other lines of
evidence and data to have a look back through the last 100 or so years since the year 1900
at the concentration of all the different greenhouse gases. So that’s carbon dioxide,
methane, nitrous oxide and other greenhouse gases such as the halocarbons and look at
what effect they have on the atmosphere over that timeframe. The left-hand graph shows
the effect they’re having in terms of radiation balance which is what we really care about
in terms of the climate. So this is expressed in watts per metre squared which is the difference
in radiation going in and out of the atmosphere and you can see the effect has been steadily
increasing. The effect of carbon dioxide is the largest, but the other ones are also very
notable. And there’s been an increase in 3.2 of those units, watts per squared metre of
energy into the climate system compared to pre-industrial times just from these long-lived
greenhouse gases we call them. The graph on the right shows the concentration in parts
per million of carbon dioxide in the blue line. They’re reaching that kind of symbolic
threshold of 400 parts per million in 2017 and now steadily above that concentration.
The red line is if we put all of the different greenhouse gases together and expressed them
in the equivalent of carbon dioxide – if they’re all carbon dioxide what effect would they
have? We call this CO2 equivalent and in 2017 we can now officially declare that, that measurement
reached the symbolic or the milestone of 500 parts per million so some of these big numbers
are being cracked in the global average of these greenhouse gases. Going to the next slide we can have a look at where the extra carbon dioxide is coming from in terms of
carbon dioxide flux and this is expressed in gigatons of carbon dioxide per year and
where it’s something is coming out of somewhere else into the atmosphere we call that a source
and when it’s going from the atmosphere into somewhere else we call that one a sink. And
here’s a measure of the different sources and sinks of carbon dioxide through time since
1900 and we can see that the majority of the sources, that’s the shapes or the colours
above the zero line, the majority is from fossil fuels and industry but there has been
some contribution also from land use change. So when we change the land that changes the
amount of carbon that the land holds or takes up. The ones below the line or the sinks where
that takes things out of the atmosphere we can see that our friend the ocean is absorbing
over 30% of the extra carbon dioxide that was in the atmosphere providing a sink. There’s
also some from the land as well. So land use change has created a source, but also the
land acts as a sink for carbon dioxide and that also reduces the concentration in the
atmosphere. And the rest is expressed in that lower light blue one which is just what remains
in the atmosphere. So… carbon dioxide is absorbed into the ocean and land, or it remains
in the atmosphere. If we didn’t have our friends the land and the ocean absorbing some of that
carbon dioxide the concentration of carbon dioxide in the atmosphere would be over 550
parts per million rather than about 400 where it is now. These plots are produced by CSIRO
in conjunction with researchers around the world under the global carbon project and
there’s a website there where you can explore the carbon budget back through time and in
different regions of the world. Okay, going to the next slide looking at the oceans as
Lynette said earlier the air temperature over Australia has risen by just over 1 degree
since the reliable national records began in 1910 and… For the oceans surrounding
Australia there’s a similar amount of warming. They’ve warmed by about 1 degree since that
same timeframe of 1910. The top graph again is expressed as the difference between sorry
the anomaly from the 1961-1990 average value so the values earlier in the century were
typically below that average, the recent ones in recent years have typically been above
that average value. And that change and that warming hasn’t been especially uniform, hasn’t
been the same everywhere and the bottom shows the recent trend in sea surface temperature
just from 1950-2017 and with warmer or redder colours showing a faster rate of temperature
increase and the yellows showing us a slightly slower rate of temperature increase and nowhere
around Australia has seen a decrease, there’s no blue colours. There’s a real hotspot in
the southeast of Australia. You can see there around the coast of Victoria and off Tasmania
and this is due to a strengthening of what we call the East Australia current. This is
a current that brings warm water down the east coast of Australia down to the norther
tip of Tasmania and that has become stronger over recent years so more warmer water is
moving south in that current creating that hotspot of faster increase in surface temperature. Okay, going to the next slide a warmer ocean on average can lead to what we call ocean
heatwaves or periods where the ocean’s surface is much warmer than average just as it does
in the air. Ocean heatwaves can be much more persistent and last for longer than atmospheric
heatwaves because of the nature of water compared to air and there’s been some very notable
marine heatwaves in the Tasman Sea and off the coast of Tasmania and in a couple of recent
years including in 2015/16 there was a recording breaking heatwave but also in ’17/’18 there
was another heatwave there, but another incident where the temperature of the ocean was very
much above average and had real impacts was in the Great Barrier Reef region and here
is a snapshot from the reef temp monitoring product at the Bureau of meteorology website
and this is temperature described as heat degree, heating days and this is integration
of many days and how much it was above average for all of those days and then put on a scale
of degrees days and you can see that a lot of this area was in the very red colours with
very high values of degrees C days compared to average and this was very closely linked
to the extensive coral bleaching in 2017 that was seen on the Great Barrier Reef and part
of that back to back coral bleaching that was seen 2 years in a row. Okay and going
to the next slide this graph I think deserves to be just as well-known and as iconic as
any temperature graph and as a description of what’s happening to our climate in recent
decades. This is the change in the total ocean heat content of the oceans. So the ocean is
absorbing over 90% of the extra energy from the enhanced greenhouse effect that we’ve
created so that means a lot of energy is going into the ocean and being stored in that water
and that has saved us from experiencing a more rapid rate of increase in temperature
on land. So this goes back to 1960 you can see early in the record there was quite a
lot of uncertainty about trends as – but as time has gone on and as there’s been improvements
to measuring methods, and there’s been a start of the very successful Argo program that Australia
has been one of the leaders of we can better measure and more accurately measure the amount
of total energy in the oceans. So the scale there is in zeta joules or 10 to the 22 joules.
Just to put that in some kind of perspective you might have eaten lunch today with a certain
amount of kilo joules in it, the measure of energy – how much energy you get in something.
This rate or this amount of energy going into the ocean in just the last few years has been
estimated at about equivalent to 3 nuclear blasts per second. That amount of energy going
into the oceans and being stored as ocean heat. And you can see in the last few decades
there has been a very steady increase. There’s a lot less variability than there is in surface
air temperature, even global average surface air temperature. There’s ups and downs and
you know, wiggles in that rate but this one is very steady especially since the year 2000
just seen a brief, strong increase and steady increase. Okay, going to the next slide… As oceans become warmer and also as ice that was on land, i.e. glaciers and ice sheets melt
and that water enters the ocean we get a rise in sea level so this is where the sea level
rises on average. Of course we get tides, and things day to day so there’s a lot of
variability in sea level but this is the sea level once you remove all of those ups, and
downs, and wiggles and this is averaged over the world and this is measured using very
accurate tide gauges and also satellite altimetry. That’s measurements from satellites. And you
can see this has been rising steadily in the last 100 or so years since 1880. Again the
measurements have become more accurate as we’ve gone through time so the uncertainty
range has narrowed a little bit and now we can compare two different independent sources
of data, the satellites, and the tide gauges as a fairly good agreement and people are looking
into why there is some difference there but the overall trend is very clear which is global
sea level has risen by over 20 centimetres since 1880 and the rate has been accelerating
in recent decades. You can see there’s a slight kind of upward bend to that line and the recent
rate is something like 3 centimetres per decade. But of course sea level rise is not experienced
the same everywhere so going to the next slide we see there’s been a different rate of rise
here around Australia in the recent decades. This is the rate of change in 1993 through
to 2017 expressed as centimetres per decade. And you can see that here the blue colours
don’t mean decrease but they just mean a lower rate or rise and you can see that in the southeast
Australia in that same area where I talked about the increased rate of warming due to
the strengthening of the East Australia Current in a similar area we see a higher rate of
sea level rise off the coast and also a hot spot in northern Australia. There are other
factors that come into play to what we actually experience in terms of sea level change at
the coast. So some places around Australia the land is also moving and some other places
around Australia there’s other regional and very local factors that come into play to
tell us what you actually experience at the cost, but this is a general picture of the
rates of change over the last couple of decades off the coast. Going to the next slide and
another side effect of increasing greenhouse gases in the atmosphere is it changes the
chemistry of the air and also of the oceans. So CO2 in the air affects plant growth and
other things, but then it also gets dissolved into the oceans and this changes the chemistry
and decreases the ph, or an increase in acidity in the ocean surface waters. Around Australia
there’s been an estimated change in ph of over 0.1 units and that may not sound very
much, but remember that ph is on a log scale, so a change from 8.2 ph to 8.1 relates to
about a 30% increase in acidity or the availability of H+ ions to do chemical reactions and if
we see further increases from say 8.1 down to 7.9 this relates to a more than 150% increase
in acidity in H+ ions. And this is having impacts and will be projected to continue
having impacts and increased impacts if that increases on animals and other organisms that
rely on calcium to build their shells as these are things like corals, but also animals with
shells. So this is kind of this other carbon dioxide problem if you like. Okay, going to
the next slide, so moving on to looking at future climate and estimating what the climate
could look like in the coming decades for Australia and for the globe let’s first look
at the tools, or some of the tools we use to estimate climate change and make projections
of future climate states. On this graph I’ve shown the observed temperature record in grey
and with a running mean put through and they’re the black lines, and the grey window behind
that is the simulations of the climate system done in Australia and around the world using
climate models. And I haven’t put an individual track of each one, but when you look at them
in aggregate you can see the range of variability and the change in trend through time and the
grey window does cover the black line. It does match that change. IF we then run those
same climate models, but without greenhouse gases or human changes we arrive at the blue
range of – blue window which doesn’t include that upward trend. So this is one like of
evidence that we use to do what we call attribution studies. This is to work out and disentangle
the different drivers of change and we just simply can’t reproduce the recent warming
using models, but also using our theories without the increase in greenhouse gases.
We can then use those same models run out into the future under scenarios of different
greenhouse gas concentration changes to make future projections of the climate and you
can see the start of those kind of projections that we’ve produced on the right-hand side
in the red window. If we were then to run those models forward and that includes all
of the different emissions scenarios out to 2030 and you can see there’s projected to
be an ongoing upward trend in temperature. Of course climate variability would come along
on top of that rising trend, but we would expect the long-term trend to sit somewhere
in that red window. Further out into the future it of course depends on which emissions scenario
we follow whether we go to a low emissions scenario or a higher one whether that rate
will continue through the rest of the century at the same rate or plateau and also marked
on this graph are some dotted lines indicating roughly what the equivalent of a 2 degrees
and a 1.5 degrees global warming above the pre-industrial level means for Australia.
It’s slightly more than the global average because land generally warms a bit more than
oceans and some areas like the southern ocean cool much less than the global average. Okay, so that’s some of the tools that we use for looking at future climate. Going to the next
slide how have we done in the past when producing climate change projections and sending out
messages about what we can expect? Well there’s been enough time now looking back to some
of the earliest communication products and analysis about what we can expect about future
climate going back to the early 1990s there was some from the IPCC, the Intergovernmental
Panel on Climate Change all the way back to 1990 and here’s a comparison for a statement
put out by CSIRO in 1992. On this black and white – no colour printed report there was
an estimated range of projected change in Australia in temperature going out to 2030
and I’ve just marked that in red and we can now see how we are tracking against that range
of change and you can see the observations have been tracking within that range, especially
that ongoing trend, the thicker back line is definitely within that red window and certainly
above the null hypothesis or the kind of defaults of no change marked there as a botted line. So for the time we would consider that to be a reliable source of information so far.
I mean we’re not at 2030 yet but it seems like it was not an unreliable kind of estimate
of what we could expect, but it was quite broad and that statement shied away from being
too confident or narrow in their projections, but what they did produce seems to be reliable.
Okay, so now going to the next slide a changing climate as Lynette kind of went through doesn’t
just mean warmer temperatures or an increase in the mean annual temperature of Australia
or in the world. It has other effects and this is a summary of some of the other effects
that we expect ongoing into the future and with more under a high emissions scenario
and those effects slightly less under a lower emissions scenario. So temperatures to rise,
sea level to continue rising, oceans around Australia to continue to warm and acidification
to continue. More hot days and fewer cool days. Tropical cyclones, there’s ongoing research
in this area and it’s still an open question but the current thinking is that we expect
a decrease in the total number, but an increase in the number of very extreme tropical cyclones
but with a lot of year to year and decade to decade variability along the way. Extreme
rainfalls especially of daily and sub-daily lengths to become more intense leading to
more flash flood. That harsher fire weather is predicted to continue for southern and
eastern Tasmania – I’m sorry, Australia and decreases in winter and spring rainfall for
southern Australia and an increase of time spent in drought but again with an ongoing
high variability. So that wraps up my sections of the webinar and so I’ll have back to Lynette.
Angela: Or Angela! Lynette: Thank you Michael and yeah I’ll pass
over to Ang to go through everyone’s questions. Angela: Absolutely thank you to everyone who
had sent questions through. I will apologize now as we have been inundated and sadly we’re
not going to have time to take everybody’s questions but we will also provide you with
an email address where you can send through any burning questions and we’ll happily address
those at a later time. So our first question today is from Clara. Clara is asking what
were the atmospheric concentrations in the 1970s? Was it a tipping point? Michael perhaps
you can take that one? Michael: So concentrations of carbon dioxide
have been steadily increasing and of course accelerating over the last kind of you know,
time since the industrial revolution in about 1750. The 1970s was a period of ongoing increase.
Reliable measurements at Cape Grim started in 1975 so we’ve got some better quality measurements
since then but yeah it was a period of increasing carbon dioxide and others. Clare: Thank you for that Michael, another question here from Liz. Liz is asking what
is the national average temperature for the baseline period? I understand it’s in the
vicinity of about 23 degrees Celsius, please confirm. Lynette perhaps if you wouldn’t mind? Lynette: I… Michael: I actually just [INAUDIBLE] it’s
21.8. Clare: Wonderful, thank you Liz for that question.
Another question here from Peter. Is the observed rainfall decline in the southeast expected
to continue as a trend, Lynette? Lynette: So I’ll start with that and then
I’ll hand over to Michael because I know he’s done work on the projections. So it is
– a lot – some of these trends that we’re seeing are trends that are predicted – projected
for the future as well and the rainfall decline across southern Australia is projected to
continue especially across that winter/spring period and southwest Australia as well. so
rainfall projections, rainfall is a lot more variable than temperature but I’ll say those
rainfall projections for southwest Australia is one of the most confident rainfall projections
that we see around the globe and we’re seeing those trends there and it really has been
projected over a number of years and iterations of models as well so I’ll pass over to Michael. Michael: I’ll just back you up on that Lynette. The southwestern Australia decline has got
a clear signal of climate change already there and is projected to continue. That’s what
globally a very kind of notable case. Southeast Australia is a bit more of an open question
about how much is due to human influence already but the projections are fairly certain, or
fairly confident about an increase in the long-term trend in the southeast of Australia
in winter rainfall but of course we’ve got to frame this in terms of very large, ongoing
natural variability. So it doesn’t mean every year it gets dryer than the last, or every
year is now a permanent drought. There’s obviously a lot of variability in Australian rainfall. Lynette: I’ll just yeah, I’ll just jump in there too Michael because I think that’s
a really important point that you just made. So we talked in our talk about the trends and
the variability happening on top of that so it’s not going to be every year it’s not going
to be the hottest year on record. We’re still going to have those warm years, cool years,
wet years, dry years but they’re happening on top of those trends now which are changing
the frequency of dry years or the frequency of those warmer years that we’re seeing. Angela: Thank you both for that and we’ve received a question from Colin also. This
is regarding oceans. There seems to be dimethane from Baths, or for Baths Strait. What was
the outlook for Melbourne, Michael? Michael: Is this in terms of sea level? Angela: I think it could be no, I think it mapped it closer to the coast. Michael: Yeah, we deliberately didn’t map it close to the coast because those local
factors can really actually affect that. So for example the area of more rapid increase
in southeast Australia is seen off the coast, but some of those local factors means that
some of those towns in the coast haven’t seen that reflected in their tide gauge changes.
So there’s other information about sea level out there and I encourage you to go look at
things like Canute, or Coast Adapt. I can send you these links to get the changes right
at the coast, but yeah we deliberately left a gap between what these satellite data can
tell us and what people’s actual experience of tide gauge is on the coast and that’s due
to various factors about what happens right at the local area. Lynette: And I’ll just jump in there too because Michael raised the point that there’s a lot
of research out there so Save the Climate of course summarizes a lot of the research
that is out there and we do have an extensive reference document available with the report
if you’re interested in following it up further. Angela: Wonderful, thank you for that. Another
question here from Clara. Clara’s asking a certification is extensively researched for
oceans, but what about freshwater ecosystems. Michael, would you like to take that one? Michael: I’m not a subject matter expert in this area at all so I wouldn’t be confident
to give you a full answer. I’m not aware of the research at all. I don’t know whether
it’s just a saltwater problem or if it’s freshwater as well. That might be something we’ll have
to get back to you. Angela: Oh yeah, absolutely Clara please send
us an email. I’ll read out the email address a little bit later in the presentation so
we can have a chat about that one. A question here from Ming. Ming is asking how is acidity
measured in oceans? Michael: So that plot showed the ph of the
oceans around Australia. That relies on measurements, but then those measurements are put together
with a model to estimate – to fill in gaps, and to fill in gaps in time and in space.
So the chemistry of the ocean is fairly well understood about what different cycles occur
and what determines the pH and the plot is based on things that are measured, but then
put together in a model to get a more complete picture. Angela: Thank you, and thank you Ming for that question. Question here from [Hamdon]
is it always ocean and atmospheric activities, or are there other indicators of climate change?
Michael, would you like to take that? Or Lynette or? Lynette: I’m happy for Michael to tackle. Angela: Michael, yeah. [INAUDIBLE] Michael: Sure, so I think it’s pretty important to realize that there’s various and fairly
independent lines of evidence that the climate is changing. So there’s measurements at weather
stations of the temperature but there’s also measurements in the ocean of temperature and
heat content. There’s measurements of things like glaciers and ice sheet changes, but the
majority of those are losing mass and are becoming smaller indicating the temperature
is rising. and there’s also other measurements of air temperature at different levels in
the atmosphere so it really is many different lines of evidence in different domains put
together that gives us a picture of a warming climate system yeah, not just the surface,
the air temperature but the oceans, ice, land, and air. Lynette: I’ll also add in too we haven’t measured it in the report, but it’s also reflected in
a number of – in natural systems that are responding to all these changes. It might
be changes in migration, changes in vegetation that we’re seeing, seasonal changes in you
know, flowering times or such. So there’s a number of lines of evidence. Angela: Thank you for that. We have time for one more question and we’ll take this one
from Peter, thank you Peter. What sort of projection is there for groundwater storage
in the future? It rarely seems to be mentioned. Lyn, any thoughts? Lynette: We haven’t gone so far as to look at groundwater storage and honestly this is
something I was thinking maybe future State of the Climates would like to look at. So
I can’t give you any confident projections on that at this stage, but I will say that
we have looked at – we do have groundwater. We measure groundwater as part of the – at
the Bureau and so in recent years we’ve been able to get – start to get that national picture
of how groundwater is changing and the groundwater reserves that we have so yeah it’s … and
I think that’s an important point as well it’s really – it really comes back to this
underlying data. You really need to have the data there that you can examine to get these
pictures so this is yeah, definitely something that we’d like to look into further. Angela: Wonderful, thank you. Lynette: Sorry, Michael Angela: Sorry Michael was there something you wanted to add? Michael: Oh, I was just going to add in a
little quick one just on top of that is so projections of rainfall, evaporation, and
water balance are an ongoing research area in CSIRO, in the Bureau and elsewhere. To
take it through to water availability and impacts on water availability and water kind of
storages and so on you need to take it to that next step of not just considering changes
to rainfall and evaporation but also what people do. So if we use a lot more, and we
draw a lot more, or less and the population demands more, and the industry demands more
that’s also a big part of what water availability is like in future. Lynette: Yeah, it’s a good point. Angela: Perfect, all right well we’ve reached
that time where Lynette if you wouldn’t mind flicking to the next slide we’ll make our
closing remarks. So for further information please take the time to read the report or
watch the accompanying videos. We have an extensive reference document that accompanies
the State of the Climate and it’s available from our website. If you would like to continue the conversation please use the hashtag #BOMWebinars in your LinkedIn posts. We’d be delighted
to hear from you. And if there is something in particular you’d like to discuss further,
or if we’ve missed your question today please email us at [email protected] next
slide please. Our next BOM webinar will be our Autumn Climate and Water Update on Thursday
the 7th of March so don’t forget to register. And that brings us to the end of our webinar
today. A big thank you to Michael and Lynette for your time and sharing your knowledge,
and to our audience. Thank you for tuning in and joining us today. We hope you enjoyed
the session and we do hope you’ll join us again next time. As mentioned earlier this
session has been recorded and we will have the video ready for your on-demand viewing
pleasure within the next week so please watch this space. Finally, but most importantly
we want your feedback. It’s our aim to bring you the highest possible quality webinars,
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