The reason for this graphic, with a thermometer showing 1 to 5 degrees C of average global heating on the left, and the extinction symbol on the right, with a symbolic rising graph from left to right, is to display as a simple iconography, the dangerous association that so many of our fossil fool national governments and international corporations reject outright from their operational consciousness.

The extinction symbol itself as been adopted and made widely known by Extension Rebellion movement.  This movement has resolved that we should tell the truth about climate change, to ourselves and the world, and change our system behaviours according to this truth.

I surprised that climate action group I belong to didn't like to use this small  symbolic version of our warming - extinction relationship., apparently because see it as being particular to the extinction rebellion group. The universal character set coding for computers, does not seem to have it. A close match is the hourglass -⧗ - U+29D7. 

The extinction symbol has an anonymous originator, see this Wikipedia Article. It first surfaced in 2011, but found no broad promotion of use. Extinction Rebellion has now taken this up as their primary in your face warming, that this is the final consequence of climate inaction. The design circle represents earth, and the hour glass represents species time, which is running out. Readers of Terry Pratchett's disk world books know the hourglass ⧗ as actual metaphysical objects, that represent each persons passing limited time in life, as carried around by the parody character of the incarnation of Death.

It is only this century that a strange "denial of death" or "terror management theory" has been found buried deep in human psyche, as one of the puzzling hidden drivers of our states of mind. Climate change denial is now another common slippery mental elision in politics. By extension, the twinned denial symbolized by  is a most difficult concept to be acted on by ordinary human minds.

I feel that the present climate emergency requires the association of rising global temperatures, with mass extinctions. This has certainly happened a number of times in earth's past history. The most recent example is documented as 5 - 8 degrees of global warming, that happened 56 million years ago, called the "Paleo - Eocene Thermal Maximum". This period of time , had high atmosphere carbon dioxide, reduced oxygen, and warm stagnant oceans. Species migrated towards the poles to escape the heat, or evolved to heat-tolerant forms, or became extinct. Overall "primary productivity" of plant kingdoms declined. Ocean and atmosphere oxygen declined. The edible parts of land plants that flourished, became less nourishing and supported smaller and fewer species of the animal kingdom. Higher rates of extinction were inevitable.

We are now very rapidly pushing our world into a similar "hot-house earth" conditions, with our rapid production of greenhouse gases from fossil fuel mining and burning, cement production and agriculture. Rising rates of extinction are happening now.

Now it we are in the race of our lives and times, to rapidly switch our civilisation from burning dead fossils, to using solar energy harvesting and storage.

[1] Extinction symbol website: https://www.extinctionsymbol.info/

[2] Current extinctions rising, Center for Biological Diversity:  https://www.biologicaldiversity.org/programs/biodiversity/elements_of_biodiversity/extinction_crisis/

[3] I/Ca evidence for upper ocean deoxygenation during the PETM:

https://www.researchgate.net/profile/Xiaoli_Zhou/publication/266323043_ICa_evidence_for_upper_ocean_deoxygenation_during_the_Paleocene-Eocene_Thermal_Maximum_PETM/links/5ab3eb840f7e9b4897c797a7/I-Ca-evidence-for-upper-ocean-deoxygenation-during-the-Paleocene-Eocene-Thermal-Maximum-PETM.pdf

[4] Global decline in ocean ventilation, oxygenation and productivity during the Paleocene-Eocene Thermal Maximum - Implications for the benthic extinction:

https://www.researchgate.net/publication/228335391_Global_decline_in_ocean_ventilation_oxygenation_and_productivity_during_the_Paleocene-Eocene_Thermal_Maximum_-_Implications_for_the_benthic_extinction