What basis has our statements

I remember my days in high school I attended a lecture of an environmental activist. At that time it was normal that allow schools outside school hours, educational lectures to his students, provided that these were organized by these groups or organizations in the city (provided that they were not hateful, unhealthy activities or other criminal activities). Climate change was just beginning to sound, and the ecological struggle of that time was nuclear power plants. The conference talked about precisely this, exactly how to stop the four nuclear power plants that were in Catalonia, and his main thesis was to seize the abandoned hydropower, which together with renewable energies would  not only stop the nuclear plants but also much of the heat plants. They were the '80 crisis and industrial activity had completely stopped alongside rivers, and consequently important parts of the mini-hydroelectric power supplied to these industries were stops.
But was activist had right? Really could we stop the Catalan nuclear plants? So I must believe it, but we can make a first attempt to see how close or far we are from the statement. Take for example the river Llobregat, river industrial for excellence, the sixth greatest river in Catalonia. This river has approximately 20 m3/s annual average flow as it passes through Martorell (so close to the Sea), his birth is 1,295 msnm approximately 1,300. Assuming that we take all the energy of the fall and considering that g ~ 10 d ~ 1000 (g gravitational constant d density in kg/m3 ) have the power from the Llobregat would  P=20x1,300x10x1,000 =260,000,000 wat also 0.26 Gwat, every nuclear power plants in Catalonia have 1 Gwat of power, therefore are required to pay a 3.8 Llobregats to stop a nuclear plant of the three that currently exist in Catalonia and the rivers similars to Llobregat there are only two; the four greatest that he fully exploited with hydroelectric and which are smaller they are very small. Obviously this calculation could be even more unfavorable if we consider that the hydroelectric performance does not exceed 65% and we should subtract the energy required to transport water for 170 km course in part that most of this course and its tributaries is below 400 m as well as the flow increases as the course progresses and 20 m3/s are at the end of this.
This example shows that fast are claims without checking. We back to the time he made these statements, we find a territory exporter of electricity with a nuclear power of 4 Gwats, where due to the economic downturn and inefficient power grid of the time ('80) it had abandoned the installations underpowered. Someone had the idea that perhaps taking advantage of better energy and re-launched small hydropower we could stop some nuclear plant, the idea was beginning to spread and at one point went from possible to secure in the end we have a speaker who was ensuring and pontificating about an issue not proven and in this case false.
The question isn't there are people making baseless assertions, the problem is that we can do it everybody, because nobody can prove absolutely everything and we must believe that the information and statements made by others have a degree of validity, which be. Our intrepid activist '80 years wasn’t lying, he exposed a truth that he knew and wanted to educate young people about this issue, and their exposure used a forceful data but which had not passed the first level of quality, to be true. This fact does not invalidate the arguments or incorrect exposure but it darkens this and it creates doubts.
In this context we have facts like climate change that are constantly called into question. No matter the countable data and studies that corroborate, the shadow of doubt remains. Data can be subject to contrary interpretations and we emphasize that we agree more depending on which side we are affiliated. But now the global data is clearly inclined towards change and the few academic voices deny them (another issue is the scope, direction or consequences). So why fail the successive conferences? The answer we must look at the amount of prejudice, statements and facts allegedly true that pollute the discourse.
When the speech leaves the academic world and it comes in the field of politics, economics and journalism; the need for clarity and precision requires headlines, and in the headlines all data have equal validity. And not only has equal validity, then the nonsense call more attention to the facts proven. So political activists, lobbies and other interested ones take arguments little contrasted that can be easily attacked in parallel, it's creating confusion leading to the current stagnation.