Source: BBC Radio 4: Today
URL: N/A
Date: 14/09/2015
Event: Julia Slingo: "So we're warming again, very much so"
Credit: BBC Radio 4
People:
John Humphrys: This year and next year will prove to be the warmest on record. You may raise an eyebrow at that, if you're one of those who asks "What happened to our summer?" but that's what research by the Met Office shows, and Professor Dame Julia Slingo is their Chief Scientist - and she's on the line, good morning to you.
Julia Slingo: Good morning, John.
John Humphrys: The warmest? Really?
Julia Slingo: Absolutely. Yes, and we think - well, very likely to be the warmest, obviously there's still some way to go, and there's always uncertainty in the observations, but this is absolutely in line with what we predicted at the end of last year, that this year could well be, if not the warmest, one of the very warmest.
John Humphrys: And then again, next year.
Julia Slingo: And again, next year. And the reasons for that are because we have a major El Nino event developing, in the tropics -
John Humphrys: Just remind us what the El Nino is - that's the current...
Julia Slingo: That's a current, it's a warm current that produces abnormally warm water along the Peruvian coast, spreading out across the Equatorial Pacific - we're currently running 2 and probably 3 degrees warmer than average, which for those parts of the world is very significant. And we know that that disturbs weather patterns around the world, and we're already seeing that, and it also elevates global mean surface temperature quite significantly.
John Humphrys: And what you're saying, as I understand it - correct me if I am wrong - is that because of the CO2 trapped in the atmosphere, more of it than there used to be -
Julia Slingo: Absolutely.
John Humphrys: - that heat will not be able to escape in the way that it might have done a thousand years ago.
Julia Slingo [after a pause]: That's not part of what we're discussing here - we're discussing we know that the heat is continually being trapped in the system, and we know that when we look at things like sea-level rise. And we've known, over the last decade, that probably more of the heat has been trapped below the surface of the ocean and therefore not seen in such a rapid rise in global surface temperatures as we've seen in the past. What we're now reporting are some quite big changes in the climate system, and heat, that heat that was trapped below the surface is now re-emerging, not only in El Nino but across the North Pacific, and leading now to quite big increases in global mean surface temperature.
John Humphrys: But -
Julia Slingo: So we're warming again, very much so.
John Humphrys: Well, we're warming again, because the other warmings that didn't happen in the way that I think it's safe to say were predicted, why were those - if, I don't know whether you would accept the word "mistakes" - but, I mean, why were those forecasts proved not to be totally accurate? I mean, a lot of people say - and including some distinguished scientists -
Julia Slingo: Yes.
John Humphrys: - these are based on computer predictions - it's all done on computers and sometimes we simply get it wrong.
Julia Slingo: Well, what we have to remember is that the Earth has its own natural variability, often on 10-year, 20-year cycles. And therefore we wouldn't expect something like global warming to be just a continuous warming process - it's overlaying these natural cycles. And the one we're talking about a lot, at the moment, is what we call the Pacific Decadal Oscillation, which was in its cold phase for at least the last decade or so -
John Humphrys: But didn't you know that was going to happen? I mean, couldn't we have been told about that, so we weren't, sort of, told we were going to bake, and when we didn't bake, people said "Well actually, it hasn't happened" and they were called climate-change deniers.
Julia Slingo: Well, I think the fact of the matter is, John, that these low-frequency variations in the ocean circulations are actually still very hard to predict, and certainly 10, 15 years ago, we wouldn't have had the observations of the current state of the ocean, and indeed an understanding of how these deep ocean circulations move heat around the system. What we've learnt in the last 15 years is that actually the ocean's playing a huge role in these decadal changes in the rate of warming, but we shouldn't use those to say that the world is still - is not warming because of greenhouse gases, we have a lot of evidence to show that the world has continued to accumulate energy, that the Arctic sea ice is still declining, that sea levels are rising, and global mean surface temperature is quite a difficult variable to talk about, because we get these natural variations showing up in the temperature record alongside the warming trend - which has not gone away.
John Humphrys: Professor Slingo, thanks a lot.
Julia Slingo: Thank you.