This #NewYear we must get serious about climate change. A big obstacle: our brains.

Current risks are vastly different from our ancestors, but our brains are wired the same. Knowing the science behind decision-making helps us better talk about climate threats & spark action. 1/

The Sixth Carbon Budget (2033-2037) charts the decisive move to zero carbon for the UK. The CCC shows that polluting emissions must fall by almost 80% by 2035, compared to 1990 levels – a big step-up in ambition. (1/12) #UKCarbonBudget 🧵

Our recommended Sixth Carbon Budget would achieve well over half of the required emissions reduction to 2050 in the next 15 years, but decisive action must start today. (2/12) #UKCarbonBudget

The recommended Sixth Carbon Budget and UK NDC also reflect the goals and requirements of the Paris Agreement, recognising the UK’s responsibility as a richer developed nation and its respective capabilities. (3/12) #UKCarbonBudget

When we recommended the UK’s #NetZero target for 2050, we demonstrated that any negative economic impact was likely to be small and the overall impact could turn out to be positive. Our analysis for this report reinforces that finding. (4/12) #UKCarbonBudget

Our estimate of the annualised resource cost (which measures the net additional cost each year to deliver the same services with lower emissions) has fallen to less than 1% of GDP through to 2050. (5/12) #UKCarbonBudget

Fascinating new paper by @AndrewDessler and colleagues arguing committed warming might be higher than expected given historical pattern effects. Its combining a lot of different concepts together, so lets spend some time disentangling them https://t.co/ILi5z515Qy

A thread: 1/19

The paper's headline number is that we previously thought the world was committed to 1.3C warming, but that number is actually over 2C (> 1.5C by 2100). This is quite a different message than we get from Earth System Models, which suggest committed warming is only ~1.2C. 2/19

This would imply that the 1.5C by 2100 target is effectively impossible, and that long-term warming of >2C would be very difficult to avoid. However, the devil is in the details, and the picture is not quite as dire as it would seem at first glance. 3/19

When we talk about "committed warming" folks are generally talking about one of two scenarios: either constant CO2 and other GHG concentrations (and forcings), or getting all emissions (or just CO2 emissions) down to zero immediately. 4/19

In the first method – constant concentrations – we find that the world warms up another 0.5C or so, as the oceans continue to take up heat as more energy is being trapped by greenhouse gases than is being emitted back to space. Much of this additional warming happens by 2100 5/19

Thread on snow ratios. The snow ratio, or snow-to-liquid ratio states how many inches of snow, when melted, yields one inch of liquid water. Ratios are usually around 10:1 or 12:1, but can vary from as little as 6:1 or as high as 30:1, or sometimes more. 1/

There's a common misunderstanding that the colder the surface temp is, the higher the snow ratio will be (fluffier snow). This is incorrect. As long is the surface temp is not close to freezing, it really doesn't matter all that much. 2/

As the surface temp gets close to or exceeds freezing, more snow is lost to melting, yielding lower ratios and heavy, wet snow. The same reasoning also applies to temps above the ground; if they exceed freezing, sleet or rain can mix with the snow, dramatically lowering ratios 3/

Much more important is the dendritic growth zone (DGZ), the layer of the atmosphere with temperatures between -12 and -18C. In this layer, snowflakes grow as dendrites, which can easily clump together into aggregates, which contain a lot of air, increasing the ratio 4/

At warmer or colder temps, the flakes grow as plates, columns, or needles, which don't clump together as well and contain less air, lowering the ratio. To make this even more complicated, there's also a dependence on atmospheric humidity. 5/