To start off, I would like to emphasize what many leading scientists and engineers have said before: never underestimate the power of human ingenuity.

What I (and they) mean by that is that time and time again humans have figured out how to solve major problems. Right now, there are many proposed solutions to stop global warming. Many of them are just considered too expensive. But there might be a point in time where the cost of the rising temperature of our home planet is much greater than the cost of different ways to cool the earth. If that time ever comes, hopefully we will be able to figure it out!

Still, to answer your question, there are some effects occurring right now, and some effects that may come in time due to the rising global temperature of the earth. One effect that has been observed is a rising water level. The oceans have risen by 8 inches in the past ~140 years (actually not primarily due to ice melting, but due to the fact that warm water expands!)

In a relatively short period of time, the temperature of the earth has risen by about 1.5 degrees Celsius. It is expected that the temperature will rise by another 1.5 degrees in the next 50 years. What will this mean for people?

Some scientists attest that there will be large changes in sea level due to these temperature change. Some scientists attest that major storms (like hurricanes) will increase in strength and number. Others have argued that such changes may not occur, but people still worry about a "runaway" greenhouse effect. This is where the amount of greenhouse gases (which trap heat and raise temperatures) increase, and then cause more greenhouse gases to be released, further increasing the temperature in an endless cycle. Some people even argue that issues such as infectious disease and poverty are more worrisome than global warming! What is clear is that the earth is heating up, and we should do something about it.

If we do nothing, and continue to rely on fossil fuels without cleaning up emissions (there are actually a lot of researchers who want to make natural gas and coal burn cleaner so we can still use these abundant energy sources without having to worry about emissions) it is possible that climate change could cause a runaway effect that is not suitable for the current state of the human race. But as I said before: never underestimate the power of human ingenuity. We are actually working to reduce our reliance on fossil fuels and are trying to clean up emissions, even with burning coal.

If we manage to corral the problems of climate change, I don't actually know what would make humankind extinct. Perhaps humans will evolve and another similar species will take over (just like homo sapiens once did.) Perhaps unpredictable problems, like super volcanoes or asteroids, will have us meeting our demise (although I would argue that we are getting pretty good at predictions and again, human ingenuity could help us solve negative effects of these problems.)

Don't let this problem worry you though - instead let it inspire you! Become a part of the solution. Conserve, reduce waste, and study. You could be the one who makes a breakthrough and solves this problem we are facing, or you could be the congressman/woman who advocates for research into this field. Everyone's help is needed, especially your's!

Global warming has many impacts. These include, but aren't limited to, rising sea level and increased coastal flooding, longer and more damaging wildfire seasons, more destructive hurricanes and an increase in extreme weather events, heavier precipitation in some places and more severe droughts in others, glacial melting, coral reef damage and even more. Whether or not it will cause the extinction of humans is a highly debated topic. It certainly has a huge impact on regions where many of the Earth's population lives, like on the coasts for example.

Rising sea levels and coastal flooding will eventually displace millions of people. Rising temperature, severe droughts and heavier rainfall also have the potential to greatly disrupt our food supply, which could cause major problems down the road. Probably one of the largest threats however to human survival is our population itself. The population of humans on Earth is rising exponentially. There are currently 7.3 billion humans on Earth and they expect that number to reach 9.5 billion by 2050. With more people, less places for them to live and less food, it could greatly impact the human race's ability to grow and move forward.