npm errors. DEPRECATION: ember-cli-babel 5.x has been deprecated. Please upgrade to at least ember-cli-babel 6.6

I upgraded from ember 2.9.0 to ember 3.4.

I am using npm install.

Now I get these deprecation errors (for some packages which I have as dependancies in package.json):

DEPRECATION: ember-cli-babel 5.x has been deprecated. Please upgrade to at least ember-cli-babel 6.6. Version 5.2.8 located: application -> ember-cli-d3 -> ember-cli-babel
DEPRECATION: ember-cli-babel 5.x has been deprecated. Please upgrade to at least ember-cli-babel 6.6. Version 5.2.8 located: application -> ember-cli-d3 -> ember-getowner-polyfill -> ember-cli-babel
DEPRECATION: ember-cli-babel 5.x has been deprecated. Please upgrade to at least ember-cli-babel 6.6. Version 5.2.8 located: application -> ember-disable-proxy-controllers -> ember-cli-babel
DEPRECATION: ember-cli-babel 5.x has been deprecated. Please upgrade to at least ember-cli-babel 6.6. Version 5.2.8 located: application -> ember-message-bus -> ember-cli-babel
DEPRECATION: ember-cli-babel 5.x has been deprecated. Please upgrade to at least ember-cli-babel 6.6. Version 5.2.8 located: application -> ember-simple-auth -> ember-cli-babel
DEPRECATION: ember-cli-babel 5.x has been deprecated. Please upgrade to at least ember-cli-babel 6.6. Version 5.2.8 located: application -> ember-simple-auth -> ember-getowner-polyfill -> ember-cli-babel
DEPRECATION: ember-cli-babel 5.x has been deprecated. Please upgrade to at least ember-cli-babel 6.6. Version 5.2.8 located: application -> ember-simple-auth-token -> ember-cli-babel

If I use yarn, the above errors go away. yarn seems to manage dependancies better and perhaps it isolates the dependancies of dependancies better? Not sure exact reason why.

Could someone explain why it works with yarn and not with npm? Also, how I can make it work with npm?

I need to make it work with npm to go live with it.