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Over our lifetimes,
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we've all contributed to climate change.
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Actions, choices and behaviors
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will have led to an increase in greenhouse gas emissions.
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And I think that that's quite a powerful thought.
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But it does have the potential to make us feel guilty
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when we think about decisions we might have made
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around where to travel to,
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how often and how,
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about the energy that we choose to use
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in our homes or in our workplaces,
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or quite simply the lifestyles that we lead and enjoy.
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But we can also turn that thought on its head,
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and think that if we've had such a profound
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but a negative impact on our climate already,
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then we have an opportunity to influence the amount of future climate change
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that we will need to adapt to.
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So we have a choice.
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We can either choose to start to take climate change seriously,
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and significantly cut and mitigate our greenhouse gas emissions,
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and then we will have to adapt to less of the climate change impacts in future.
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Alternatively, we can continue to really ignore the climate change problem.
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But if we do that, we are also choosing
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to adapt to very much more powerful climate impacts in future.
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And not only that.
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As people who live in countries with high per capita emissions,
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we're making that choice on behalf of others as well.
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But the choice that we don't have
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is a no climate change future.
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Over the last two decades,
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our government negotiators and policymakers have been coming together
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to discuss climate change,
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and they've been focused on avoiding a two-degree centigrade warming
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above pre-industrial levels.
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That's the temperature that's associated with dangerous impacts
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across a range of different indicators,
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to humans and to the environment.
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So two degrees centigrade constitutes dangerous climate change.
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But dangerous climate change can be subjective.
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So if we think about an extreme weather event
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that might happen in some part of the world,
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and if that happens in a part of the world where there is good infrastructure,
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where there are people that are well-insured and so on,
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then that impact can be disruptive.
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It can cause upset, it could cause cost.
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It could even cause some deaths.
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But if that exact same weather event happens in a part of the world
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where there is poor infrastructure,
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or where people are not well-insured,
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or they're not having good support networks,
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then that same climate change impact could be devastating.
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It could cause a significant loss of home,
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but it could also cause significant amounts of death.
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So this is a graph of the CO2 emissions at the left-hand side
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from fossil fuel and industry,
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and time from before the Industrial Revolution
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out towards the present day.
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And what's immediately striking about this
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is that emissions have been growing exponentially.
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If we focus in on a shorter period of time from 1950,
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we have established in 1988
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the Intergovernmental Panel on Climate Change,
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the Rio Earth Summit in 1992,
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then rolling on a few years, in 2009 we had the Copenhagen Accord,
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where it established avoiding a two-degree temperature rise
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in keeping with the science and on the basis of equity.
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And then in 2012, we had the Rio+20 event.
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And all the way through, during all of these meetings
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and many others as well,
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emissions have continued to rise.
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And if we focus on our historical emission trend in recent years,
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and we put that together with our understanding
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of the direction of travel in our global economy,
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then we are much more on track
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for a four-degree centigrade global warming
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than we are for the two-degree centigrade.
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Now, let's just pause for a moment
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and think about this four-degree global average temperature.
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Most of our planet is actually made up of the sea.
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Now, because the sea has a greater thermal inertia than the land,
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the average temperatures over land are actually going to be higher
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than they are over the sea.
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The second thing is that we as human beings don't experience
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global average temperatures.
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We experience hot days, cold days,
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rainy days, especially if you live in Manchester like me.
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So now put yourself in a city center.
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Imagine somewhere in the world:
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Mumbai, Beijing, New York, London.
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It's the hottest day that you've ever experienced.
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There's sun beating down,
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there's concrete and glass all around you.
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Now imagine that same day --
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but it's six, eight, maybe 10 to 12 degrees warmer
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on that day during that heat wave.
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That's the kind of thing we're going to experience
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under a four-degree global average temperature scenario.
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And the problem with these extremes,
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and not just the temperature extremes,
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but also the extremes in terms of storms and other climate impacts,
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is our infrastructure is just not set up to deal with these sorts of events.
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So our roads and our rail networks
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have been designed to last for a long time
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and withstand only certain amounts of impacts
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in different parts of the world.
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And this is going to be extremely challenged.
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Our power stations are expected to be cooled by water
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to a certain temperature to remain effective and resilient.
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And our buildings are designed to be comfortable
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within a particular temperature range.
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And this is all going to be significantly challenged
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under a four-degree-type scenario.
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Our infrastructure has not been designed to cope with this.
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So if we go back, also thinking about four degrees,
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it's not just the direct impacts,
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but also some indirect impacts.
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So if we take food security, for example.
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Maize and wheat yields
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in some parts of the world
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are expected to be up to 40 percent lower
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under a four-degree scenario,
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rice up to 30 percent lower.
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This will be absolutely devastating for global food security.
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So all in all, the kinds of impacts anticipated
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under this four-degree centigrade scenario
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are going to be incompatible with global organized living.
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So back to our trajectories and our graphs of four degrees and two degrees.
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Is it reasonable still to focus on the two-degree path?
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There are quite a lot of my colleagues and other scientists
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who would say that it's now too late to avoid a two-degree warming.
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But I would just like to draw on my own research
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on energy systems, on food systems,
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aviation and also shipping,
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just to say that I think there is still a small fighting chance
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of avoiding this two-degree dangerous climate change.
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But we really need to get to grips with the numbers
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to work out how to do it.
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So if you focus in on this trajectory and these graphs,
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the yellow circle there highlights that the departure
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from the red four-degree pathway
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to the two-degree green pathway is immediate.
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And that's because of cumulative emissions,
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or the carbon budget.
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So in other words, because of the lights and the projectors
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that are on in this room right now,
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the CO2 that is going into our atmosphere
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as a result of that electricity consumption
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lasts a very long time.
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Some of it will be in our atmosphere for a century, maybe much longer.
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It will accumulate, and greenhouse gases tend to be cumulative.
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And that tells us something about these trajectories.
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First of all, it tells us that it's the area under these curves that matter,
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not where we reach at a particular date in future.
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And that's important, because it doesn't matter
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if we come up with some amazing whiz-bang technology
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to sort out our energy problem on the last day of 2049,
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just in the nick of time to sort things out.
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Because in the meantime, emissions will have accumulated.
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So if we continue on this red, four-degree centigrade scenario pathway,
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the longer we continue on it,
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that will need to be made up for in later years
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to keep the same carbon budget, to keep the same area under the curve,
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which means that that trajectory, the red one there, becomes steeper.
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So in other words, if we don't reduce emissions in the short to medium term,
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then we'll have to make more significant year-on-year emission reductions.
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We also know that we have to decarbonize our energy system.
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But if we don't start to cut emissions in the short to medium term,
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then we will have to do that even sooner.
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So this poses really big challenges for us.
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The other thing it does is tells us something about energy policy.
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If you live in a part of the world where per capita emissions are already high,
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it points us towards reducing energy demand.
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And that's because with all the will in the world,
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the large-scale engineering infrastructure
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that we need to roll out rapidly
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to decarbonize the supply side of our energy system
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is just simply not going to happen in time.
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So it doesn't matter whether we choose nuclear power
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or carbon capture and storage,
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upscale our biofuel production,
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or go for a much bigger roll-out of wind turbines and wave turbines.
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All of that will take time.
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So because it's the area under the curve that matters,
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we need to focus on energy efficiency,
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but also on energy conservation -- in other words, using less energy.
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And if we do that, that also means
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that as we continue to roll out the supply-side technology,
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we will have less of a job to do if we've actually managed
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to reduce our energy consumption,
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because we will then need less infrastructure on the supply side.
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Another issue that we really need to grapple with
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is the issue of well-being and equity.
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There are many parts of the world where the standard of living needs to rise.
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Bbut with energy systems currently reliant on fossil fuel,
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as those economies grow so will emissions.
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And now, if we're all constrained by the same amount of carbon budget,
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that means that if some parts of the world's emissions are needing to rise,
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then other parts of the world's emissions need to reduce.
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So that poses very significant challenges for wealthy nations.
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Because according to our research,
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if you're in a country where per capita emissions are really high --
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so North America, Europe, Australia --
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emissions reductions of the order of 10 percent per year,
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and starting immediately, will be required for a good chance
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of avoiding the two-degree target.
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Let me just put that into context.
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The economist Nicholas Stern
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said that emission reductions of more than one percent per year
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had only ever been associated with economic recession or upheaval.
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So this poses huge challenges for the issue of economic growth,
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because if we have our high carbon infrastructure in place,
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it means that if our economies grow,
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then so do our emissions.
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So I'd just like to take a quote from a paper
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by myself and Kevin Anderson back in 2011
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where we said that to avoid the two-degree framing of dangerous climate change,
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economic growth needs to be exchanged at least temporarily
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for a period of planned austerity in wealthy nations.
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This is a really difficult message to take,
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because what it suggests is that we really need to do things differently.
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This is not about just incremental change.
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This is about doing things differently, about whole system change,
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and sometimes it's about doing less things.
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And this applies to all of us,
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whatever sphere of influence we have.
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So it could be from writing to our local politician
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to talking to our boss at work or being the boss at work,
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or talking with our friends and family, or, quite simply, changing our lifestyles.
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Because we really need to make significant change.
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At the moment, we're choosing a four-degree scenario.
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If we really want to avoid the two-degree scenario,
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there really is no time like the present to act.
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Thank you.
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(Applause)
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Bruno Giussani: Alice, basically what you're saying,
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the talk is, unless wealthy nations start cutting 10 percent per year
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the emissions now, this year, not in 2020 or '25,
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we are going to go straight to the four-plus-degree scenario.
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I am wondering what's your take on the cut by 70 percent for 2070.
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Alice Bows-Larkin: Yeah, it's just nowhere near enough to avoid two degrees.