No.

Most of the preceding responses have overlooked one relatively-recently identified home for life on the planet; within the crust itself. Researchers have found bacteria up to 4 kilometers down in continental crust and 2 km beneath oceanic crust. Recent estimates are that up to 70% of the microbial life on the planet is, in fact, in the deep biosphere.

That being the case, in order to sterilize the planet you'd need to heat the crust so that the heat penetrates down far enough to ensure there was no space between the hot rocks above and the hot rocks below for any life to survive. To do it quickly means dumping so much heat into the crust to allow it to work it's way down that you're almost certainly talking about creating a magma ocean on the surface.

There is no human technology capable of this, and will not be by 2025. While, theoretically, you might be able to slowly shift the orbit of, say, the Moon to do it through impact (and I'm not sure even that will be enough), it's not happening within 6 years.

Well, the one thing that life needs on Earth (and pretty much anywhere else depending on how extreme your xenobiology is) is water.

Now, we're not trying to boil the ocean here but...

No wait. That's exactly what we need to do.

Let's start with how much water that is to boil. We're talking about 1.26 x 10²¹ litres of the stuff. That's a lot and is going to need a lot of energy to boil off. Exactly how much? Well, it takes approximately 4200 J to heat a litre of water by 1 °C, so it will take around 420 kJ to heat it by 100 °C.

Now, I know this is a simplification, and you're going to say things like 'Hey, the water on earth is warmer than zero degrees' and 'Hey, that doesn't account for the energy used in state change for ice at the poles' and 'Hey, what about pressure differential at the bottom of the ocean?' etc. and you're right; I'm over simplifying but for the purposes of an answer that doesn't blow the field limit of the answer box, let's just assume that on average we're going to need 420 kJ per litre of water on Earth to boil it off.

In practical terms, that means we're going to need 5.292 × 10²⁶ joules to boil off the ocean. But that's just for starters; what we don't want is that water condensing again, so we want to keep up a supply of joules to basically keep it as steam in the atmosphere. But we'll get to that.

There is no such thing as an average nuclear reactor, but the largest one in the US is capable of generating just under 4 MW. Let's assume that we're building reactors half that size and we have a reactor that can reliably produce 2 MW of power 24/7. That is the equivalent of 48 GWh a day.

Now, 1 MWh = 3.6 × 10⁹ J meaning that our nuclear power plant can generate 1.73 × 10¹⁴ J. Extending this further, we need around 3 × 10¹² power plants to do this work in a day.

But, we have a month! So, dividing by 30, we now only need 10¹¹ power plants to do it. The good news is that for that month, we're only going to need 4.5 tonnes of nuclear fuel per power plant to do this, although we may need more later to keep the water as steam for an unspecified period of time. But here's the thing; the world becomes unlivable because of the ambient temperatures well within the 30 days, so all 'complex' life is already dead. Most of the simpler life is either struggling or dead as well, so let's assume that we only need fuel for our 30 days.

According to some sources, there is only around 40 trillion tonnes, or 4 × 10¹⁰ tonnes on the planet today, which works out a little less than 10% of what we need to do this (10¹¹ reactors times 4.5 tonnes of fuel). But, it's not 2025 yet! And there's another source of heat that we can potentially tap; the earth's mantle.

It is already estimated that the leakage of heat from the mantle is around 47 TW, and we can accelerate that through deep core drilling. Essentially, we want to drill a whole bunch of deep holes around the earth, right down to the mantle and let out the lava. This is already a thing, and geothermal energy producers are already getting output that rivals some nuclear power plants. In practice this means that we can generate 10% of the power through nuclear, and between now and 2025 invest a lot of money into geothermal research and drill deep holes that generate the other 90% of the heat we need through tapping into the earth itself.

This secondary (actually, primary given it needs to comprise 90%) method of heat generation has an added bonus; it's likely going to destabilise the tectonic plates as well given the number of holes we're going to drill.

In any event, the point is that life dies without liquid water. If we want to deliberately destroy life on this planet in 2025, the only thing we need by then in terms of tech is drilling technology; we have everything else we need, and we also get to do the one thing I keep getting told I'm not allowed to do on my regular projects;

Boil the ocean.

No

Within a month period is impossible. The only event realistically capable of wiping out all life that quickly is a meteor strike and you can't get to any asteroid big enough in that time frame let alone get it moving and back to Earth.

Scientists estimate it requires something of at least 100km diameter for an extinction level event. The Chicxulub impactor was 11 to 81 km and only wiped out the dinosaurs.

In the early history of the Earth (about four billion years ago),
bolide impacts were almost certainly common since the Solar System
contained far more discrete bodies than at present. Such impacts could
have included strikes by asteroids hundreds of kilometers in diameter,
with explosions so powerful that they vaporized all the Earth's
oceans. It was not until this heavy bombardment slackened that life
appears to have begun to evolve on Earth.

Wikipedia

Bacterial life is extremely hard to kill

You need a longer timeframe or perhaps settling for killing higher life forms? (Which in a month would still be virtually impossible)

TL;DR: We are unable to kill all life even in a tiny piece of medical equipment. Don't expect us to perform better at killing all life on the whole Earth.

We are already trying hard to kill all life in limited settings and with all the might of 2019 technology there is always something remaining. For example, in high-risk applications, we we don't try to remove the last millionth of microbes.

Of course, when killing all life on Earth we have the advantage that preserving it is not a requirement and we can go with more destructive methods than for medical equipment. However, even with lots of nukes, the size of the crust and the oceans makes any large scale sterilizing method less powerful than any industrial standard to sterilize smaller objects.

Grey Goo

One possible way that life on the planet could be extinguished is a Grey Goo scenario. Some kind of self-replicating nano-machine that indiscriminately consumes bio-matter could in theory wipe out all life on the planet, and assuming it propagates at 8 m/s (assuming I did the math right) it could entirely encompass the earth in a month. This assumes of course there's no built in failsafe, and it has expanded to a large enough area that it can't be stopped with conventional explosives, and or nukes. This also assumes it is only started in a single place. Even with a slower propagation rate, if it was released in multiple places around the globe simultaneously it could still suffice to end everything. It's worth noting that while a Grey Goo scenario could become unstoppable, in all likelihood it would propagate at a much more sedate pace.

Math section

Circumference of Earth: 40,075,000 meters

Seconds in a month: 2592000

8 * 2592000 = 20736000 (half the circumference, since it would be expanding in all directions).

< How to kill a Tardigrade >

Life is stronger than many people may have expected. For some, unless you nuke them on the head, they'll survive most world destruction events.

One example is Tardigrade. Known to have cyptobiosis, they can suspend their metabolism. They can survive under extreme environments that would kill almost any other animal.

(mostly from wiki)

• Low temperature: few to days at 73K, few minutes at 1K.


• High temperature: few minutes at 151°C.


• Extreme pressure: vaccum of open space and solar radiation combined for at least 10 days, or more than 1200 Atm.


• Dehydration: survive 10 years of dry state.


• Radiation: Tardigrades can withstand 1,000 times more radiation than other animals.

While their average life span is only a few month, they can be dehydrated to skip a rather long time period, so they can just chill and wait until the "kill" is over.

And there are bacteria that live undersea (3,650 meters) and withstand extremely high temperature (121 Celsius). I highly doubt if you can damage them effectively, let alone eliminate them.

Given the time restriction you set (year 2025), no I don't think it is possible to kill ALL life on earth.

Supervolcanos

Supervolcanos are bad things. Very bad things. One supervolcano can qualify as a global catastrophic risk, creating a layer of ash in the sky across a continent, and a theory places a global winter 75,000 years ago as a result of one. Now, one supervolcano can't guarantee an extinction level event. Well, that's one.

There's more than one, though. A supervolcano, by definition, is anything that can qualify as a class 8 Volcanic Explosivity Index. And, from a few searches on the subject, there's around a dozen potential candidates scattered around the globe. Plus a few Class 7s, which aren't really extinction level events, but we might as well add them to the fire anyway.

Then we get to the main problem - triggering this event. This one's fun. Now, we've got two ways of doing it. The first is to just nuke it repeatedly until it explodes. (Like, maybe ten nukes to a supervolcano? Followed up by a few hundred round of conventional warheads, like MOABs. That seems like a reasonable number.) Now, I'm not sure if it'll work. In fact, I'm fairly certain that this won't trigger a conventional volcanic eruption. But you'll definitely get all that nice red-hotlava and ash, and hopefully the force of the explosion will scatter in to the winds.

The second way of doing things is hiring a geologist and using seismic charges to manipulate the crust. You'll probably need sizable charges, maybe even a few nukes, but this time strategically to trigger the volcano, rather than brute force. I am not a geologist, so my knowledge ends here, but there should be a way to set something like that up, given a few hundred nukes and five years to dig.

In either event, what you end up with is an ash-shell in the atmosphere, thick enough to block all sunlight and the heat that comes with it, choking life as we know it. Within days, the Earth becomes a horrific hellscape of either frozen barren wastes, or lava-choked scorched Earth. To clarify, there will be a few humans who survive past a month, presumably some important people with bunkers, or something of the like. But the Earth is done for. You'll have to wait for it to reset.

Since there are no practical "yes" answers I'll give a partial answer--meets everything but the 2025 requirement.

Send a mission to the asteroid belt, they're carrying a big load of nukes. The objective is to use them as an Orion drive to divert an asteroid towards Earth.

Blofeld does the "burn" while the asteroid is behind the sun so no pesky astronomer could notice what's going on. After the burn is done the asteroid is painted black so it's not going to be noticed as it comes down. It's aimed for a barely grazing trajectory.

As it approaches Blofeld makes his ransom demand--pay up if you want the crew to use the last of their nukes to nudge it into a near miss rather than a grazing hit. Orbital mechanics waits for no man so there can be no delaying tactics with the negotiations. One month from impact is the last point where they can nudge it away without simply shattering it instead.

The science:

Orion is going to take a lot of engineering but all the principles have been proven to work. A chemically powered version has actually flown a short distance and objects have been demonstrated to be able to survive in close proximity to a nuclear detonation.

Blofeld will deliberately choose an asteroid with no structural strength to ensure Earth can't simply use massive numbers of bombs. If you thump a rubble pile it's basically going to come apart. Some bits will be lost but so long as the thump isn't too hard the self gravity of the bits will bring them back together. This is a slow process, though, limiting the rate at which you can thump it. Thump it too hard and fast and it flies apart--now you have a great collection of rubble that you can't hope to divert. It will still deliver just as much energy when it hits, though, and the objective is that energy, not the destruction of the impact.

Note that the engineering is probably going to be done in the not too distant future. Delta-v doesn't care if it's used for good or bad, the exact same technology could be used to divert a rock that threatens Earth and the ability to move asteroids this way vastly exceeds any other proposal out there--when time is short there will be no other option. (Not to mention every other asteroid deflection technique requires rendezvous, Orion doesn't. So long as the guidance unit is good enough you merely need to get the bombs to the desired standoff range, it doesn't matter if they're doing a head-on approach.)

I don't think it can be done in any way imaginable save for complete physical destruction of the planet. Bacteria are essentially impossible to kill.

So, a possible extinction-level event that would kill anything big and possibly eventually a lot of bacteria too:
"Sun shade" around the Earth. Just make eternal eclipse. No sun = no life. Eventually. I believe extinction-level event will happen within a month due to mass die-off of stuff requiring sunlight. Actual complete extinction will not be even close in that time frame and you might not wipe a single species if you turn the shade off after just a month - it will just look like extinction happened in a month due to massive die-off at that time.

(you can achieve sunblocking effect with volcanoes/meteors, possibly nukes to some extent, but this manmade shade looks more in spirit with the question demanding purposeful trigger of the extinction)

Now, what about bacteria? As another somewhat related SE question asked (https://biology.stackexchange.com/questions/23050/organisms-using-thermal-energy-as-their-sole-energy-source), there are bacteria that live ONLY on heat, so even if you turn off the sunlight "forever", these will survive until Earth cools down.

Now, how long will it take before Earth cools down completely because we cut off the sun - well, assuming Earth is rock-ish, we have 1 kJ/kg*K and its size gives about 10^27 J/K. Well, if I didn't screw up several orders of magnitude.
We have about 10^17 W incoming from the sun that keeps Earth in heat balance and that is now gone, so we have 10^17 W of cooling. We are looking at 10^10s/K = about 30 years to drop a single degree. Note that the surface will cool much faster than the interior, but at the bottom of an ocean trench it will still take a while before those bacteria die off.

A strangelet could do the job

Of course it is not hard science, because these things are (still) only theoretical and a doomsday scenario would require that some assumptions are right.

According to the wikipedia page about stangelets

A strangelet is a hypothetical particle consisting of a bound state of roughly equal numbers of up, down, and strange quarks. An equivalent description is that a strangelet is a small fragment of strange matter, small enough to be considered a particle.

and

If the strange matter hypothesis is correct and a stable negatively-charged strangelet with a surface tension larger than the aforementioned critical value exists, then a larger strangelet would be more stable than a smaller one. One speculation that has resulted from the idea is that a strangelet coming into contact with a lump of ordinary matter could convert the ordinary matter to strange matter.[15][16] This "ice-nine"-like disaster scenario is as follows: one strangelet hits a nucleus, catalyzing its immediate conversion to strange matter. This liberates energy, producing a larger, more stable strangelet, which in turn hits another nucleus, catalyzing its conversion to strange matter. In the end, all the nuclei of all the atoms of Earth are converted, and Earth is reduced to a hot, large lump of strange matter, the size of an asteroid.

So, if someone has enough resources to build the most powerful particle accelerator in the world in 6 years (1), and some theories prove to be correct, he could trigger an end-of-the-world scenario with the total destruction of life on Earth.(2)

(1) Note that if the purpose is the destruction of the world, it would be relatively quick to build, since the biggest part of the work in projecting and building an accelerator is to be able to perform experiments, which would be useless in this case

(2) But of course, even given a powerful enough accelerator, the possibility that such thing could happen in real life are in the range of "win the national lottery 100 times in a row"

Mass Extinction

Life on Earth has recovered from five mass extinction events. Definition: more than 75% of species become extinct. The closest life came to being ended completely was "the great dying" of the late Permian mass extinction which eliminated 96% of extant species and nearly ended life completely.

In this 20,000 year period a huge volcanic eruption in Siberia released large amounts of CO2 into the atmosphere. Methanogenic bacteria thrived from this CO2 plume and began contributing large amounts of methane [another greenhouse gas] into the atmosphere as well. Global temperaturs rose and oceans acidified, losing oxygen and killing fish life. This in turn released hydrogen sulfide or H2S. H2S displaces oxygen and is highly toxic to aerobic life. It was in short a radical transformation of our atmosphere and oceans to a point where they no longer supported the vast majority of extant species.

As to how you could do that on purpose using existing man-made technology? I don't think you can. Technically we are in the anthropocene 6th mass extinction, where the cause is human activity but even at our worst we aren't recreating the conditions of the Permian event. Volcanism releases far more CO2 naturally than we can on purpose and to get a bloom of methanogenic bacteria and possibly oceanic algae blooms all synchronised at once.. you'd need to know when an eruption as bad if not worse than Mount St Helen was going to occur and have stocks of the bateria ready to disperse. If you knew a way hands down to cause a volcanic eruption that bad you'd be close but it would certainly take longer than a month.

You could make a snowball earth using environmental chemistry, make the sky dark and kill 99% of the planets land and sea animals, but it would be difficult. Humans can make nuclear bombs 10,000 to 20,000 times Hiroshima for every bomb. Each bomb could take the worlds temperature down 1'C, if you buried it somewhere where it generates atmospheric ash, so you can potentially cool the planet by 100'C. Krakatoa took the temperature down 1.2 degrees, and it was only worth one human megabomb, i.e. 3 Tsar bombs.

If you can lift 1000 cubic kilometers of ash into the air, that's already at least 20'C or 30'C degrees drop in temperature. Humans should be able to lift about 10km3 with every bomb, so you'd need at least 100 bombs.

There is a lot of ash in Indonesia, Hawaii, and other archipelagos.

If you made as many atomic bombs as man can make, say a thousand of them, in the time given, and bury them all in places with dark ash, coal, volcanoes, you can probably trigger a darkness and nuclear winter which would destroy most of the plants, land animals and fish. After that, the small mammals, insects and mushrooms will always survive for at least a few hundred years. You could also try to manufacture botulin and sarin gas and other toxic hyper-variants in billions of tons, and combine both a snowball earth and the chemical warfare, but it would only give the planet a brief sleepy period, and then it would bounce back as good as new.

Push the earth closer to the Sun!

I came up with this idea that may achieve that evil goal, with current technology and billions of rocket engines, in 117 years; although that doesn't suffice the requirement, I'd like to discuss with people to see if there is a better approach.

The basic idea is: using rockets to decelerate the earth so that it will get closer to the sun. As it gets close enough, I expect the "pale blue dot" becomes a "bright red dot". If the whole planet becomes (almost) a lava orb, I don't think any life-form can survive that - and no, it's not destroying the earth, so definitely not overkill. Earth just returned to a form 4.5 billion years ago.

A slightly detailed version:

• I plan to use Saturn-V, the most powerful rocket in human history.


• I will use Hohmann transfer orbit to move earth between two orbits. That's when I realized we can't achieve this plan in a timely manner.


• I want the new radius to be 0.1 AU. Apparently, Mercury at 0.3 AU is not hot enough for project lava orb (700 Kelvin).

Math time:

some constants

# AU distance, m

au=1.496e11

# Gravitational constant, m^3*kg^-1*s^-2

G=6.67408e-11

# weight of the earth, kg

M=5.972e24



r1 = au

r2 = 0.1 * au

mu = G * M



pi=3.14



F = 3.3e7

How long does it take?

According to Hohmann transfer orbit wiki page (yup, just learned this 5 minutes ago), this process will take 117 years to make the orbital transfer

t_h = pi * ( (r1+r2)**3 / (8*mu) )**0.5 # 117 years

What is the change of speed in each process?

Hohmann transfer requires a two-step speed change. Delta_v of each process is surprisingly small - 29m/s and 56m/s decrease in speed.

delta_v1 = ((mu/r1)**0.5) * (((2*r2)/(r1+r2))**0.5 - 1) # -29.6 m/s

delta_v2 = ((mu/r2)**0.5) * (1 - ((2*r1)/(r1+r2))**0.5) # -56.9 m/s

How can we achieve that!

I plan to use Saturn_V (with Rocketdyne F-1 engine), THE rocket that sent Apollo XI to the moon. I disregarded the time needed to construct and assemble these rockets.

Assume we have precisely one year for the first deceleration and the second deceleration, how many Saturn_Vs do we need to ignite at the same time to achieve the Hohmann transfer?

burn_1 = (M * -delta_v1) / (F * 86400 * 365) # 1.7e11

burn_2 = (M * -delta_v2) / (F * 86400 * 365) # 3.3e11

Whoa! 170 Billion and 330 billion rockets, not including the amount of kerosene fuel wasted in this process. This will most likely tear the atmosphere into pieces, destroy the ionosphere (hello solar wind), and heat generated in this process should be able to eliminate most life forms already.

conclusion

Project lava orb will literally take hundreds of billions of rocket engines, and 117 years to push the earth close enough to kill all life on earth. This project is based on an unreliable calculation, an unrealistic waste of resources, and 20-century technology.

But hey, we did it!

The best way to answer the question, assuming the means of extermination is by nuclear bombs or other similar weapons of mass destruction is to compare what is being sought for with what has actually happened in the past. Since life is still on the Earth, then this gives you a lower bound on what is required.

Yellowstone's volcano was about 875,000 megatons when it last went up.

The dinosaur comet was about 100,000,000 megatons.

TNT Equivalent (with list of examples):
https://en.wikipedia.org/wiki/TNT_equivalent

Here are the most recent snapshot of bomb counts
https://www.armscontrol.org/factsheets/Nuclearweaponswhohaswhat
Russia and the US have a 6000-7000 each, everyone else has a few here and there. It adds up to about 15000. The biggest Cold War nuke was around 100 megatons, so that gets you up to a max of 15,000,000 megatons; but more likely around something like 1,000,000 megatons.

That's not even scratching the surface. It barely even matches Yellowstone. You have a long way to go.

In contrast, take a look at what happens (according to Universe Sandbox 2) when our resident Evil Wannabe God-Demiurge gets into another one of his moods and puts a 1 millimeter-sized black hole next to the Earth. https://www.youtube.com/watch?v=h3KOmt9onvc

Well... this is highly theoretical and very speculative, but I think it still qualifies as hard science. It could be possible that our universe is in a "false vacuum" state and given the right conditions could collapse to a state of a lower energy. If this was happen to one small place, the theory is that it would spread like a "bubble" at the speed of light. You literally wouldn't see it coming. And after it has happened, the universe (in that place) would have changed with all new laws of physics and fundamental constants. Pretty sure that life as we know it wouldn't exist anymore. Heck, chemistry wouldn't exist anymore.

But, as I said, it's highly theoretical at this point and we have no idea if this is actually the case or not. But it does work for a story.

It might be.

It has been considered, as very hard science, here.

Synopsis: you would need to drop a hydrogen bomb into the sun. Deep into the sun. The problem, therefore, is to avoid the bomb being vaporised before it reaches sufficient depth to start a nuclear chain reaction within the hydrogen of the sun itself. Whether a sufficient thickness of sufficiently heat-resistant ablative material might be created and delivered into the sun, seems unlikely, but I'd prefer to have seen a proof of total impossibility.

(On the political/human front, it probably is impossible. How to hide your intent? It would just take one person out of many tens of thousands involved in such a project to sabotage it, and it's not as if you can test it properly in advance!)

We can try to adopt the method proposed here to prevent a large impact with the Earth, to let large proto-planets like Vesta or Ceres crash into the Earth, but it is unlikely to work on a time scale of just a few years. A relatively fast way could be by sending a mission to a a few comets to alter their courses to make them crash into large asteroids the size of Eros. Those collisions are engineered such that these large asteroids are sent to collide with minor planets like Vesta and Ceres in such a way that these minor planets will collide with the Earth.

This is a yes or no, open-ended question, where you specifically ask for hard science. I believe that, even though the majority have answered no, there is no way you could truly claim that it is impossible. You cannot prove a negative, as they say. That being said, I'd like to explore one particular path of action that might result in the earth being uninhabitable.

Colliding the moon with the earth.

I think it's safe to say that this would end all life, likely within hours. https://www.iflscience.com/space/what-would-happen-if-moon-hit-earth/

So the big question then, is can you do it in a 30 day period?

Google tells me that the energy required to stop the moons orbit around the earth is about 3.7e28 joules. That is quite a lot more than the entire nuclear arsenal of the earth. (according to google)

Now, it depends a bit on what exactly you mean by your 30 day period. If you were to produce this thrust with a rocket engine (with sufficient propellant somehow) spread out over the entire 30 days, you would have to produce roughly 1e26 watts of thrust. I believe that means you would be looking at the equivalent of roughly 5e20 f1 rocket engines on the moons surface, as well as their fuel for continuous burning for 30 days, which doesn't seem particularly feasible.

If you also had to take from the 30 days to manufacture, transport and install these rocket engines (and their fuel) it would be even more difficult. You would probably have to find a way to do most of this on the moon itself. Especially using the moon as propellant would help the equation a lot. I don't really know of any way to do that.

So my answer is: This particular method seems infeasible. (aka no)

As other answers have pointed out, humans do not and will not have the technology to do so. That leaves non-human technology. Although you've stated that you don't want to physically destroy the Earth, considering life in the cust, the only way to kill all life on Earth is to essentially make the Earth stop being.

Those aliens must be already en-route in order to get here by 2025. They are powerful. Very powerful. Any sufficiently advanced technology is indistinguishable from magic. Their spaceship is planet sized, and although 25 trillion tons of antimatter is costly, spaceship policy requires the destruction of any planet harboring intelligent life. It takes the aliens about 3 gigaseconds (~100 years) to produce such a bomb, but they've known for 15 gigaseconds that they are going to pass near enough the Earth to target it with one, and it's been many teraseconds since they last had to neutralise an entire planet (for safety and regulatory reasons, they don't stock more than a few billion tons of antimatter). They send off their 25 trillion tons of antimatter on a course to hit the Earth at 0.9c. After it hits, the Earth physically blows into pieces. Any life that isn't killed yet, will be soon by boiling, by vacuum, or by lack of water. And if any microbes survive even that, they wouldn't be life on Earth anymore. They would be life on a second asteroid belt in solar orbit.

ATMOSPHERIC INTERVENTION

without protection, everything will face judgement

It's entirely possible, however, it's not a "noah's flood". Things will die slowly, but completely.

Location

This is important, as you'll need a thick, forested area where there is plenty of foliage. I recommend the American/ Canadian Midwest, or the vast, low-population Russian forests.

Preparation
The goal here is to strip the atmosphere of all protective qualities. This means that we have to reach a global supercritical temperature, where the earth becomes so hot it strips itself of an atmosphere. How hot is that? An average day temp of 100C will slowly ebb the oceans away, and once the oceans are gone, life will go. You'll also need to stockpile Flourine. The world puts out 5,000,000 Tons of Florine a year. Let's say that we put 1/2 of that (in the 10 year span) towards destruction, or 100,000,000 Tons. Let's put the entirety of that into carbon tetraflouride, where 1 molecule of said compound has the effect of 7350 molecules of CO2, and lasts many times longer.

We can do better, though. Sulfur hexaflouride, most notable for the deep voice it gives you upon breathing it in, is 400% more potent than Flouromethane, with only 50% more cost (sulfur quantity availability is much more than Florine). On top of that, it's atmospheric lifetime is 3,200 years, so it's rather static. With 100 megatons of Florine, that comes out to the equivalent of 1.986 Teratons of CO2 for the first 20 years. To compare, our CO2 output estimate for 2018, that's 50 years of CO2 output in a few moments.

That's not enough, maybe to kill all land animals, but not most creatures in the sea.

See, Sulfur hexafloride just heats the planet, there is still protection provided by the atmosphere. For that, we're going to use a different compound: Halon 1301. This chemical is used in fire extinguishers to fight chemical fires, and we could reasonably produce 1.81 million tons, given the limited capacity of Bromine production of 250,000 tons per year. This is capable of eliminating 1,310 megatons of ozone. Compare the 1.81 million tons figure with the 790 tons of 1301 released in 1997. Releasing this quantity of 1301 would be the equivalent of 2291 years of pollution (we used CFC aerosols for 50 years).

The event

Here's a prediction from NASA of of the ozone concentration if we continued using CFCs for another 60 years:

The damage above would be only 5.24% of the total possible damage such an event would cause.

With ozone being out of the equation, Ionizing radiation is much more common on earth now, along global warming being 50 years more advanced. by no accurate calculation, I'd estimate a global temp increase of about 15C because of the Sulfur release alone.

The atmosphere is now toxic

Normal life cannot exist using the atmosphere for air, as ionizing radiation can now liberate atoms from the surface to create spontaneous gasses.

The Oceans are now toxic

As the atmosphere befalls to this, so does the ocean, and oxygenation from algae is no longer possible.

The Oceans are now super-salinated

As water evaporates off in extreme heat, the concentration of salts and minerals in the water skyrockets, killing off most creatures.

The surface is now dust

eventually, all non-human land creatures succumb to drought or kidney failure. what's left of the surface is inorganic structures, and dust.

The ocean is nearly uninhabitable

With the exception of extremophiles, all life in the ocean is gone.

Humanity's final Hurrah: The nuclear anthem

with all food being gone except twinkies, humanity decides it's time to set off the nukes (though the nukes were on a timer since you released the gas). They launch and race into the plasma that's shortly above everyone's heads. With all nuclear bombs at hand, the major targets are: The Chile super volcano, The Wyoming super volcano, and a few more in the Philippines, along with any remaining human settlements.

With a little luck, over 15,000 cubic kilometers of mass, or 0.00000178% of it's total mass, but that figure isn't important, what is important is that the mantle now has open ejection channels, and that the crust, is more or less, sinking, and weakening the magnetic field of the earth.

eventually, the earth turns into a clone of Venus, with acid rains, slowed days, extreme heat, and most importantly, no life. Even the extremophiles have no means of reproduction, as their environment has changed so much. a sterile planet.

edit:
This is not a 30-day extinction event, but rather an event in 30 days that tips the dominoes towards impending doom. It's unlikely that anything would go extinct as a result of the events in the first 30 days.