Pep Canadell Profile picture
Aug 29, 2021 7 tweets 4 min read Read on X
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1/n

Australia ranks 6th in the world in the amount of forest area, with about 134 Mha (FAO 2020), after Russia, Brazil, Canada…, the countries where you might think forests really are, not in the dry Australian continent.

Keep reading if interested Image
2/n

Although Australia does have extensive, diverse and beautiful forests, the very large area claimed is because of the decision by the Government to report forest extent based on forests equal or taller than 2 m, while the rest of the countries report on taller than 5 m. Image
3/n

@qinyw_OU @XiangmingXiao @matin_brandt @ciais @pepcanadell ++ have produced a forest map based on radar (PALSAR) and optical (MODIS) data using 5 m height to have an extent more comparable with other countries. Image
4/n

That gives an area of 32 Mha of forests for the year 2010, compared with 149 Mha reported by the Government.

See paper and data links:
bit.ly/3t6vbNv
5/n

There are reasons for the choice of 2 m over 5 m, including perhaps that the FAO forest definition is a Northern Hemisphere view of what a forest should look like. Image
6/6

In the end, definitions need to serve their purpose in the first place (structure, function, biodiversity, resources).

And regardless of the forest definition, even single trees outside of forests play an important role.

Paper:
nature.com/articles/s4159…
And speaking of beautiful forests in Australia, the photo in the first tweet in this thread, here repeated, is from the Atherton Tablelands in Queensland. Image

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More from @pepcanadell

Jun 11, 2024
1/10

@gcarbonproject has just published the most comprehensive Global Nitrous Oxide Budget to date.

Global N2O emissions continue to grow largely driven by the increase in the use of chemical nitrogen fertilizers and the production of animal manure.

doi.org/10.5194/essd-1…
2/10

N2O is the third most important GHG after CO2 & CH4.

Accounts for 6.5% of the GHG radiative forcing.

It is 273 times more powerful than CO2 (100y timeframe).

Once emitted, N2O stays in the atmosphere for 117 years, and therefore its climate impacts are long-lived. Image
3/10

The concentration of atmospheric N2O reached 336 parts per billion in 2022 (the latest year with a global average), 25% above pre-industrial levels.

N2O is also an ozone-depleting substance, and its rise further delays the recovery of the stratospheric ozone hole. Image
Read 10 tweets
Mar 9, 2023
THREAD

We talk a lot about tipping points in the Climate System, yet we have so little hard evidence

In @BoZheng18 et al, we report a sharp tipping point of climatic drought in the boreal region, which has led to an exponential increase in fire CO2 emissions over the past 10ys
2/4

Although many ecological thresholds have already been identified in response to climate change (see: ), few have been demonstrated at scales that matter to the global climate.
3/4

The implication of this boreal tipping point certainly justifies further attention.

The 2021 emissions peak, on a trend initiated 10 years ago, was the single largest fire CO2 emission event of the last two decades, more than twice larger than the Australian fires in 2019
Read 4 tweets
May 31, 2022
Thread
1/10

This figure is one of the many great figures of IPCC AR6 WGI

It is the first time in 30 years+ of IPCC that a fig. on carbon sinks is published in the Summary for Policy Makers, the one document with most readers, including governments, & often the only one read.
2/10

According to Earth System Models, cumulat. C sinks will be larger with higher emissions to 2100, even including the hottest scenario

The growth in atmospheric CO2 drives the increased sinks, which offsets and surpasses the negative impacts of climate, particularly warming
3/10

However, the total fraction of emissions removed by the land and ocean sinks is smaller in higher emission scenarios. That is, we get relatively more help from nature in low emission scenarios than in high emission scenarios.
Read 10 tweets
May 11, 2022
Thread
1/5

IPCC infographics of the three most important GHG BUDGETS:

CO2, CH4, N2O

They include the main anthropogenic and natural sources and sinks.
2/5
Carbon Budget

Fossil fuels are the dominant anthropogenic source

Large natural fluxes sensitive to climate change

Of all CO2 emitted to the atmosphere from human activities:

46% accumulates in atmosphere
23% taken by ocean
31% stored in terrestrial ecosystems
3/5
CH4 Budget

Extraction, transport & use of fossil CH4, & livestock (domesticated ruminant animals) are equally dominant anthropogenic sources.

Freshwaters & wetlands are the dominant natural sources, both with very large uncertainties & sensitive to climate change
Read 5 tweets
May 9, 2022
THE CONTEXT

It is unequivocal that the increases in atmospheric CO2, CH4, & N2O since pre-industrial are caused by human activities.

The 3 GHGs are responsible for 2/3 of global warming, with synthetic gases, carbon monoxide, and black carbon responsible for the rest.

Fig5.4 Image
Current atmospheric concentrations of CO2, CH4 and N2O are higher than at any point in the last 800,000 years. For CO2, concentrations are unprecedented in the last 2 million years.

Ch5, Fig. 5.3 Image
Equally important but less discussed is the rate at which CO2 concentrations are changing now

10x faster than any other time during the last 800,00 yrs;
4-5x faster than during the last 56 Myrs.

These high velocities leave us with no analog in the paleorecord to study impacts Image
Read 5 tweets
Nov 27, 2021
Thread
1/n

Our new assessment of forest fires in Australia shows a multi-decadal increase in the burned area and a markedly increase in mega-fire years burning more than 1 million hectares.

nature.com/articles/s4146…
@NatureComms
2/n

We analyzed trends in the burned area using satellite + ground-based observations and in 9 wildfire risk factors and indices that relate to characteristics of fire weather, extreme fire behaviour, fuel loads, and ignition for forests in Australia.
3/n

Forest burned area has increased linearly over the past three decades at a rate of 48,000 ha/yr.

Comparing 1988-2001 with 2002-2019, the mean burned area had increased by 350% before the Black Summer fires (2019) and by 500-800% when including 2019.
Read 14 tweets

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