Scotsman columnist Ian Johnston speaks to climate specialist Dr Samantha Burgess of the Copernicus Climate Change Service
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00:00Hello, my name is Ian Johnston, I'm a Scotsman journalist and today I'm delighted to be joined
00:04by Dr Samantha Burgess, the Deputy Director of the Copernicus Climate Change Service to talk
00:09about the effects of global warming on the oceans and how the two are interacting. Thanks very much
00:15for speaking to me and welcome. Thank you so much Ian. Cool, so this is obviously quite a big subject
00:23but if you could briefly explain how the oceans have been responding to increasing carbon emissions
00:28and the rise of global temperatures just to set the sort of background of the situation. So the ocean
00:36plays a really important role in climate change and in the impacts of climate change on our planet,
00:43so the ocean so far has absorbed about 90 percent of the excess heat from climate change that's been
00:50caused by people and about 50 percent of the extra carbon in that's been emitted into the atmosphere
00:57from human activities and the implications of this extra heat and extra carbon lead to a number of
01:04different things. So it's changing ocean circulation, it's changing sea levels by warming the ocean as
01:12well as by melting ice on land, it's changing sea ice so we have less sea ice than we did historically
01:19and it's changing the ecology of the ocean and it's changing weather patterns as well. A lot of our weather
01:26patterns are driven by the ocean so the physics, the chemistry and the biology of the ocean have all been
01:34impacted by climate change. So when you're talking about the warming of the oceans there, that's
01:39that's changing the sea level because the warmer water expands, is that right? Yes, that's right. So
01:47there's thermal expansion which is directly from water being warmer and this also changes the chemistry of the ocean
01:55the ocean because warmer water also has the ability to carry less nutrients in it. So we get things like
02:03oxygen minimum zones and it has implications for food cycles when warmer water carries less nutrients in it.
02:11Okay okay and then so kind of the reason I was wanting to talk to you about is basically this sort of strange event that happened in May 2023
02:25because I noticed that the graphs showing that average ocean temperatures tend to follow a fairly
02:32regular seasonal pattern with a sort of peak in around March and then a smaller peak around August
02:38but May 2023 this kind of changed and just looking at as a lay person if it was dated from a machine I might
02:45think that something had snapped or a widget had worn out. Can you explain what happened? Yes, so in part
02:53there's a seasonal cycle in the ocean due to the seasonality of our planet so we have more ocean in the
03:01southern hemisphere and that's why we see the peak in ocean temperatures at the end of the southern
03:08hemisphere summer so in February and March time. However, when we're looking at the maximum global
03:16temperature for our planet, the peak is actually July-August and that's because land is warming up
03:22faster than the ocean and we have more land in the northern hemisphere so that is responding to the
03:28seasonal cycle of the the northern hemisphere so we also have a smaller peak in July-August time where
03:36we see the northern hemisphere ocean getting warm as well and what we observed in 2023 was a departure
03:45from this seasonality where we saw really strong anomalies or a departure from the normal ocean
03:55temperature towards the the middle and end of 2023. This was when we had a El Nino event going on in the
04:04Pacific Ocean and it led to record high ocean temperatures in all the ocean basins so not just in the
04:13Pacific but in the Atlantic and the Indian in the southern ocean as well and the reality is for the
04:19last two years we've seen continue to see these exceptional temperatures in the ocean. So do we have
04:28an idea of why that particularly happened? I mean there have been El Nino news before but the the the
04:34pattern seems fairly regular was this a was this a departure that sort of happened before or was it
04:39particularly big departure or? It was a new departure so we've seen changes in ocean temperatures through
04:49time and if we look at a graph looking at the the history of sea surface temperatures
04:58the ocean and how much that's departed from the climatological average of the last 30 years we
05:06can see in the early part of this period that starts in the 1980s we've got bluer colours so the ocean is
05:13much cooler was much cooler than it is right now up until the 2000s the 2010s but we see for the last
05:2215 years or so we're seeing those red temperatures come in and we can see the really exceptional
05:28temperatures that we saw in 2023 and 2024 so we can see from this figure that it's quite bumpy so we
05:36have seen a lot of variation in the the ocean temperatures so we can see the the scale on the left
05:46hand side it's in degrees celsius and ultimately the ocean is bouncing around a half a degree above
05:53average and a half a degree below average but we've seen in the last two years a stronger departure from
06:01average so we've not seen that type of signal before that strength of signal and scientists are still
06:10trying to under understand why uh we saw such a departure with a el nino event that wasn't particularly
06:18strong um so we have el nino events um they're they're a regular event they're part of the natural
06:25cycle of our planet they happen every three to seven years and um one of the interesting things about
06:33the 2020 2023 event was that we had a a three-year period or what's known as a triple dip la nina which
06:43is the cooler phase of this el nino and oscillation cycle but it really surprised a lot of scientists
06:51this departure from average and and why we're seeing these record high temperatures in the ocean
06:57and we're still seeing scientific analyses come out as to try and explain why this is okay and so uh
07:05presumably in may last year people were looking out for will this happen again but it seemed to to my
07:12eyes anyway to return to kind of the normal pattern but a higher level um and and and will you be will
07:19you be kind of sitting up a night looking at what's happening with the data that comes in in the next
07:25few weeks yeah so when we look at may 2024 we um the el nino event that kind of uh was one of the
07:35triggers for these exceptional ocean temperatures peaked at the end of 2023 and we know that the the
07:42impact of the el nino lags from when the event peaks so we anticipated in 2024 that we'd see these record
07:51high ocean temperatures because the lag from the event but when we look at 2025 where we are in neutral
08:00what's termed and so neutral or el nino southern oscillation neutral conditions so the the driver isn't
08:08creating extra warmth or extra cooling but we're still seeing second highest level ocean temperatures
08:17so that's very interesting i and you my team at the Copernicus climate change service are certainly
08:23monitoring the ocean temperatures very closely to understand whether they'll continue to cool over
08:29the next couple of months like they have done historically or whether we'll continue to see
08:34exceptional temperatures like we have for the last two years okay okay and how significant how important
08:41is what's happening in the oceans to climate change in general the ocean is really important for climate
08:48change and uh climate change impacts the the physics the chemistry and the biology of the ocean so if
08:56if we stick with the physics for the time being a warmer ocean leads to more evaporation which leads to
09:03more um uh moisture in the atmosphere so when storms form they um uh form more intensely with more
09:12intense rainfall it means there's more energy available for for cyclones hurricanes um typhoons depending
09:21on which ocean basin you're in so we know that a warmer ocean creates more intense storms we know the
09:27chemistry of the ocean changes because a warmer ocean uh has uh less carrying capacity or less ability to carry
09:36nutrients so we see things like oxygen minimum zones which leads to fish deaths which has huge implications for
09:45aquaculture so for fish farming uh around the world and it also changes the uh ocean acidity so the the
09:54chemistry of the ocean we rely on a lot of organisms that calcify so coral reefs um calcify um shellfish
10:05calcify their shells as well so when the ocean becomes more acidic it's much harder for those organisms to
10:12calcify uh also when the ocean is warmer it disrupts ocean circulation so we know um through looking at the
10:22historical measurements of different ocean currents that those ocean currents have slowed down historically
10:30speaking over the past and and some of those ocean currents like around antarctica and also in the
10:36north atlantic um the estimates are that they've slowed down between 10 and 20 percent okay and many
10:42people will have heard about tipping points so one of the tipping points in the ocean is for ecosystems so
10:50um if we get up to two degrees of warming it's um predicted that we'll lose coral reefs and other
10:58calcifying organisms if we get up to two degrees of warming um it's predicted to significantly disrupt
11:06our ocean circulation as well and in the uk in particular um we're much warmer than we would be
11:14due to warm ocean currents keeping our temperature quite mild yes i was just gonna ask you about that
11:21because um i i've heard it said that you know if if we had we're on the same kind of latitude as
11:26labrador in canada so we could end up with a climate more like theirs than the one we have at the moment
11:32which is quite sunny um uh today anyway but um is that is a is that a bit of a worry would change our
11:39agriculture quite substantially yes exactly so um many people may remember the the um hollywood disaster
11:47film the day after tomorrow uh which had the so that's obviously disaster movie it's not based on
11:55science um but the the precursor for that disaster was the um the north atlantic uh circulation turning
12:04off uh which led to rapid cooling um so that it isn't what the science said but there is a real risk
12:13that um with a slowing down of ocean currents we would anticipate seeing much cooler temperatures
12:20impacting europe which would be much more similar to those that are on the other side of the atlantic
12:26that canada faces for example yes i think i remember a scene from that in which the sort of hero is being
12:32chased by the cold and they had to run into a building very quickly indeed so probably not as
12:37dramatic as as that in real life perhaps but definitely not and then do we understand what's
12:43going on in the oceans well enough or are there kind of uh significant uncertainties could could the
12:49could there be a another surprise like in may 2023 um is this a sort of sleeping giant that we are
12:56awakening in some way really good question as a scientist i would always say um that uh no we don't
13:04understand it well enough when we look at ocean observations um we only have the ability to observe
13:12the the top 2000 meters of the ocean we rely on satellites to understand the changes in the surface
13:21of the ocean and then we have autonomous vehicles that um measure the top 2000 meters so we can tell
13:29that the surface of the ocean that has changed a lot uh and the um interior of the ocean has also
13:36changed but we don't have the ability to measure the deep ocean so our models suggest that's also
13:43warming up as well but at a slower rate than the surface ocean and we definitely need more data to
13:49understand how the ocean is changing at depth and how what implications that has for um for the
13:58physics of the ocean but also for for the biology that we depend on from the ocean yes i what one thing
14:05i i this is a general impression as an environment correspondent is that um scientists are very careful
14:12to stick to the evidence and what we know but i sometimes wonder whether that can lead to an
14:18underestimate of what could happen if you see i mean do you do you think that's true or do you think
14:24we've got uh do you think the kind of estimates that scientists have produced about climate change and
14:30its effects are are pretty accurate or how would you describe the accuracy of those so filled with
14:38uncertainties of course yeah so really important question and certainty or confidence in what the data is
14:47telling us is telling us is really important and when we look at international documents like the
14:55intergovernmental panel on climate change um that last produced a report in 2021 um the sixth assessment
15:03report that um goes through a incredibly robust review process um because it's approved by governments around the
15:14world and uh there's uh hundreds of scientists that input into the the evidence base there and uh the
15:24assessment of the confidence levels from the ipcc so intergovernmental panel on climate change
15:31assessment reports have to be really robust so when you look at an individual paper in the literature
15:39that's written by a much smaller group of scientists they would often have a different confidence level
15:46but these big assessment reports are really taking all of the information and assessing a confidence or a
15:55certainty level on some of the predictions and and they use very specific language so things like you know the
16:02human impact on climate change is unequivocable that it's it's us it's our fault uh we are doing it but equally we
16:12have the ability to make different choices to change our impact in the future um when we look at the future
16:20impacts so when we project out to 2050 or 2100 our confidence decreases on uh and our confidence decreases
16:31because it depends on our choices now so at the moment we've got a certain emission scenario which
16:38lead to a certain amount of warming and depending on what happens this decade will really change
16:46our confidence and our assessments of what is more probable than not going forward in the future
16:53and that's why these assessment reports are repeated every seven to ten years to really make sure
16:59the scientific evidence is reassessed and that that information is shared with governments as a new
17:06up-to-date assessment of the the scientific certainty what's well known and well understood and what
17:13still is developing and and how our projections of the future are changing okay so i mean is there anything
17:21else anything sort of big area of ocean climate science that we've missed or that you think it would be
17:27worthwhile knowing about oh that's a lots of things yeah that's a fascinating question i think they
17:36you know so one of the the challenges associated with the ocean is that uh it is an incredibly
17:44biodiverse ecosystem ecosystem and but uh everything that lives in the ocean generally speaking has a um incredibly
17:54finite or narrow ecological niche um so fish species that we like to eat in the uk for example they have a you
18:05know something like a four degree temperature range of water that they like to live in um and often they like to
18:11live uh in that water temperature because that's where their prey is found so we're really seeing
18:18disruptions in um the whole ocean ecosystem where uh species are moving further north in the northern
18:26hemisphere so we're getting uh tropical species like tuna being observed more frequently around the uk because
18:34the water the water the waters are warming we're also seeing heat waves in the ocean um so extreme marine
18:42heat waves uh have the ability to uh or have the the impact of causing mass mortality events um so we're
18:50really trying to understand how the ocean is changing with climate change and what implications that has for
18:56ocean biodiversity and for ocean currents and for the the implications for weather patterns as well okay
19:04so over the next few weeks are you like me going to be checking the the copernicus website to see what
19:10the data coming through on sea surface temperature to see if they do the normal pattern or if there's
19:16something weird going on yes yeah so it's one of my favorite websites too so i look at it on a weekly basis to
19:23really see how sea surface temperature is changing through time so at the moment we've got a bit of an
19:29uptick um but it's one of those fascinating things that because it's a average over the whole ocean it can
19:36change very rapidly um and yeah i i and my team are watching it really closely to really understand
19:45when we move into may and june so move into the the northern hemisphere summer how the ocean will respond
19:52and what impacts this has for um temperatures over the summer as well and and for um storm generation
20:01great okay um well thank you very much indeed for speaking to me it's been a fascinating chat and uh
20:07i've learned lots about uh what's going on in the ocean so um thank you very much indeed for
20:12agreeing to come and talk to us thanks for the invitation and great discussion ian cheers cheers all the best
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