Future Cimate (Week 6) - Post 2

Future Climate

          Global climate change is here, what society does in the next thirty years will define the future of the ecosystem. The biggest source of uncertainty about future climate is what humans are going to do; scientists have spent time predicting the future in different ways, however no one actually knows what the future holds. The global ecosystem has a climate sensitivity number, this number defines how much global temperature will rise per net amount of carbon emissions. The general scientific consensus is that for every one-thousand gigatons, one billion tons, of carbon emitted the global temperature will rise by one point eight degrees Celsius. So for every one-thousand one-hundred gigatons of carbon emitted the temperature will rise by two degrees Celsius. Currently ninety-seven percent of scientists say climate change is real, those scientists also agree that an increase in temperature by two degrees is a critical point. Meaning that anything beyond two degrees will be a worldwide disaster. That leaves the human race with an emissions budget. Humans have one-thousand one hundred gigatons to emit before we push the ecosystem past its tipping point. As of where humans are in this emissions budget: since the beginning of the industrial revolution humans have emitted five-hundred and forty gigatons of carbon. That leaves five-hundred and sixty gigatons left to emit before the temperature rise is pushed passed two degrees. This number is incredibly important and it leaves scientists with an equally important question: If, and when will humans reach this budget? The answers lie with climate prediction models. Each model predicts a certain pathway for human emissions. There are two main types of models that each approach this goal from a different way, however, both deal with a factor called radiative forcing. Radiative forcing is the measure of influence a certain factor, like polar ice or volcanic eruptions, has on the balance of incoming and outgoing energy in the ecosystem. It also measures the importance of each of these factors in relation to potential climate change. The first type of prediction model is the Special Report on Emission Scenarios, or SRESs. These scenarios start by defining different possible human choices, and then deciding likely emission pathways for radiative forcing levels. As the next model type RCPs have more opportunity for accuracy and specification, they have mostly eclipsed SRES's in the IPCC's official reports. RCPs, or Representative Concentration Pathways are used to project different future pathways of human carbon emissions. These projections start by defining specific endpoints for radative forcing at a point in the future, currently the most common RCPs have projections going to twenty-one hundred. These models work backwards in predicting the human emission pathways that will get to those endpoints. Currently the IPCC has four possible RCPs. As an example, there is RCP 8.5, which has radiative forcing ending at eight point five watts per meter squared in twenty-one hundred. This means that by twenty-one hundred about eight point five watts per meter squared more energy will be added to the climate than pre-industrial values. For this scenario to happen humans would need to increase annual emissions from about ten gigatons to almost thirty gigatons. This is often dubbed the business as usual scenario, because it goes along with the increasing emissions trend happening currently. This RCP is on the higher end of the four possible scenarios. Each of these four representative concentration pathways has humans reaching the carbon emission budget at a different time. RCP eight point five has humans using up the budget of five-hundred and sixty gigatons of carbon by twenty forty-eight. The lowest RCP, RCP three- peak and decline, RCP3PD, has emissions increasing to three watts per meter squared and then declining, this scenario does not use up the budget before it begins declining. 

          The future is unknown, but the possibilities are shown through these models. Whether the human race uses up the emission budget in the next thirty years or humans never reaches that budget is entirely up to the choices made in the next few years. It is up to humans to decide if the critical point will be reached. Global climate change is real, and it is happening now. The human race may have dug its own grave in just thirty years. That is why it is imperative that actions of mitigation are taken now, while there is still an opportunity to make change. Once that critical point is reached, there is no way to reverse its effects. Humans have the choice to mitigate or to adapt, but if things do not change quickly, mitigation may no longer be an option.